Also avoid recomputation of memberType in findMembers

Also avoid recomputation of memberType in findMembers

Swathes of important logic are duplicated between `findMember`
and `findMembers` after this run of optimization.

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in reflection. Also fixed test case that failed when moving to findMember
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This commit updates `findMembers` with the bug fixes that `findMember`
has received, and adds flashing warning signs for future maintainers.

A followup commit will address the duplication at the root.

Exclude them from superclasses in `findMember` and in
`OverridingPairs`.

The odd logic in `findMember` that considered whether the
selector class was owned by the owner of the candidate private
symbol dates back to 2007 (bff4268), but does not appear to
have any relationship to the spec.

Refinement types are still able to inherit private members from
all direct parents, as was needed in pos/t2399.scala. More tests
are included for this scenario.

In short, the logic now:

 - includes direct parents of refinements,
 - otherwise, excludes privates after the first class in the
   base class sequence

TODO: Swathes of important logic are duplicated between `findMember`
and `findMembers` after this run of optimization.

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in reflection. Als
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

Swathes of important logic are duplicated between `findMember`
and `findMembers` after they separated on grounds of irreconcilable
differences about how fast they should run:

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This didn't actually bear fruit, and the intervening years have
seen the implementations drift.

Now is the time to reunite them under the banner of `FindMemberBase`.

Each has a separate subclass to customise the behaviour. This is
primarily used by `findMember` to cache member types and to assemble
the resulting list of symbols in an low-allocation manner.

While there I have introduced some polymorphic calls, the call sites
are only bi-morphic, and our typical pattern of compilation involves
far more `findMember` calls, so I expect that JIT will keep the
virtual call cost to an absolute minimum.

Test results have been updated now that `findMembers` correctly
excludes constructors and doesn't inherit privates.

Coming up next: we can actually fix SI-7475!

Swathes of important logic are duplicated between `findMember`
and `findMembers` after they separated on grounds of irreconcilable
differences about how fast they should run:

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This didn't actually bear fruit, and the intervening years have
seen the implementations drift.

Now is the time to reunite them under the banner of `FindMemberBase`.

Each has a separate subclass to customise the behaviour. This is
primarily used by `findMember` to cache member types and to assemble
the resulting list of symbols in an low-allocation manner.

While there I have introduced some polymorphic calls, the call sites
are only bi-morphic, and our typical pattern of compilation involves
far more `findMember` calls, so I expect that JIT will keep the
virtual call cost to an absolute minimum.

Test results have been updated now that `findMembers` correctly
excludes constructors and doesn't inherit privates.

Coming up next: we can actually fix SI-7475!

Swathes of important logic are duplicated between `findMember`
and `findMembers` after they separated on grounds of irreconcilable
differences about how fast they should run:

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This didn't actually bear fruit, and the intervening years have
seen the implementations drift.

Now is the time to reunite them under the banner of `FindMemberBase`.

Each has a separate subclass to customise the behaviour. This is
primarily used by `findMember` to cache member types and to assemble
the resulting list of symbols in an low-allocation manner.

While there I have introduced some polymorphic calls, the call sites
are only bi-morphic, and our typical pattern of compilation involves
far more `findMember` calls, so I expect that JIT will keep the
virtual call cost to an absolute minimum.

Test results have been updated now that `findMembers` correctly
excludes constructors and doesn't inherit privates.

Coming up next: we can actually fix SI-7475!

Swathes of important logic are duplicated between `findMember`
and `findMembers` after they separated on grounds of irreconcilable
differences about how fast they should run:

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This didn't actually bear fruit, and the intervening years have
seen the implementations drift.

Now is the time to reunite them under the banner of `FindMemberBase`.

Each has a separate subclass to customise the behaviour. This is
primarily used by `findMember` to cache member types and to assemble
the resulting list of symbols in an low-allocation manner.

While there I have introduced some polymorphic calls, the call sites
are only bi-morphic, and our typical pattern of compilation involves
far more `findMember` calls, so I expect that JIT will keep the
virtual call cost to an absolute minimum.

Test results have been updated now that `findMembers` correctly
excludes constructors and doesn't inherit privates.

Coming up next: we can actually fix SI-7475!

Swathes of important logic are duplicated between `findMember`
and `findMembers` after they separated on grounds of irreconcilable
differences about how fast they should run:

    d905558 Variation #10 to optimze findMember
    fcb0c01 Attempt #9 to opimize findMember.
    71d2ceb Attempt #8 to opimize findMember.
    77e5692 Attempty #7 to optimize findMember
    275115e Fixing problem that caused fingerprints to fail in
    e94252e Attemmpt #6 to optimize findMember
    73e61b8 Attempt #5 to optimize findMember.
    04f0b65 Attempt #4 to optimize findMember
    0e3c70f Attempt #3 to optimize findMember
    41f4497 Attempt #2 to optimize findMember
    1a73aa0 Attempt #1 to optimize findMember

This didn't actually bear fruit, and the intervening years have
seen the implementations drift.

Now is the time to reunite them under the banner of `FindMemberBase`.

Each has a separate subclass to customise the behaviour. This is
primarily used by `findMember` to cache member types and to assemble
the resulting list of symbols in an low-allocation manner.

While there I have introduced some polymorphic calls, the call sites
are only bi-morphic, and our typical pattern of compilation involves
far more `findMember` calls, so I expect that JIT will keep the
virtual call cost to an absolute minimum.

Test results have been updated now that `findMembers` correctly
excludes constructors and doesn't inherit privates.

Coming up next: we can actually fix SI-7475!

Validate against 2.11.0-SNAPSHOT

SI-6502 Convert test to asserts

Calls to synthetic case class apply methods are inlined to the
underlying constructor invocation in refchecks.

However, this can lead to accessibility errors if the constructor
is private.

This commit ensures that the constructor is at least as accessible
as the apply method before performing this tranform.

I've manually checked that other the optimization still works in other
cases:

scala> class CaseApply { Some(42)  }
defined class CaseApply

    scala> :javap -c CaseApply
    Compiled from "<console>"
    public class CaseApply {
      public CaseApply();
        Code:
           0: aload_0
           1: invokespecial #9                  // Method java/lang/Object."<init>":()V
           4: new           #11                 // class scala/Some
           7: dup
           8: bipush        42
          10: invokestatic  #17                 // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
          13: invokespecial #20                 // Method scala/Some."<init>":(Ljava/lang/Object;)V
          16: pop
          17: return
    }

Rewrite usages of procedure syntax