…ce structs (swiftlang#76903)

The thunk's parameter needs the @in_guaranteed convention if it's a
const reference parameter. However, that convention wasn't being used
because clang importer was removing the const reference from the
type and SILGen was computing the type of the parameter based on the
type without const reference.

This commit fixes the bug by passing the clang function type to
SILDeclRef so that it can be used to compute the correct thunk type.

This fixes a crash when a closure is passed to a C function taking a
pointer to a function that has a const reference struct parameter.

This recommits e074426 with fixes to
serialization/deserialization of function types. The fixes prevent clang
types of functions from being dropped during serialization.

rdar://131321096

… reference structs (#76903)"

This reverts commit 9c44b79.

The commit caused swift's deserialization code to crash.

rdar://138726860

… reference structs (#76903)" (#77309)

This reverts commit 9c44b79.

The commit caused swift's deserialization code to crash.

rdar://138726860

…ed const reference structs (#76903)" (#77309)"

This reverts commit f73c2e5.

…ed const reference structs (#76903)" (#77309)"

This reverts commit f73c2e5.

…ed const reference structs (#76903)" (#77309)"

This reverts commit f73c2e5.

…ce structs

This PR is another attempt at landing #76903. The changes compared to
the original PR:
* Instead of increasing the size of SILDeclRef, store the necessary type
  information in the conversion AST nodes.
* The PR above introduced a crash during indexing system modules that
  references foreign types coming from modules imported as
  implementation only. These entities are implementation details so they
  do not need to be included during serialization. This PR adds a test
  and adds logic to exclude such clang types in the serialization
  process.

rdar://131321096&141786724

…ce structs

This PR is another attempt at landing #76903. The changes compared to
the original PR:
* Instead of increasing the size of SILDeclRef, store the necessary type
  information in the conversion AST nodes.
* The PR above introduced a crash during indexing system modules that
  references foreign types coming from modules imported as
  implementation only. These entities are implementation details so they
  do not need to be included during serialization. This PR adds a test
  and adds logic to exclude such clang types in the serialization
  process.

rdar://131321096&141786724

…ce structs

This PR is another attempt at landing swiftlang#76903. The changes compared to
the original PR:
* Instead of increasing the size of SILDeclRef, store the necessary type
  information in the conversion AST nodes.
* The PR above introduced a crash during indexing system modules that
  references foreign types coming from modules imported as
  implementation only. These entities are implementation details so they
  do not need to be included during serialization. This PR adds a test
  and adds logic to exclude such clang types in the serialization
  process.

rdar://131321096&141786724

…ce structs

This PR is another attempt at landing swiftlang#76903. The changes compared to
the original PR:
* Instead of increasing the size of SILDeclRef, store the necessary type
  information in the conversion AST nodes.
* The PR above introduced a crash during indexing system modules that
  references foreign types coming from modules imported as
  implementation only. These entities are implementation details so they
  do not need to be included during serialization. This PR adds a test
  and adds logic to exclude such clang types in the serialization
  process.

rdar://131321096&141786724

…ce structs

This PR is another attempt at landing swiftlang#76903. The changes compared to
the original PR:
* Instead of increasing the size of SILDeclRef, store the necessary type
  information in a side channel using withClosureTypeInfo.
* Rely on SGFContext to get the right ClangType
* Extend BridgingConversion with an AbstractionPattern to store the
  original clang type.
* The PR above introduced a crash during indexing system modules that
  references foreign types coming from modules imported as
  implementation only. These entities are implementation details so they
  do not need to be included during serialization. This PR adds a test
  and adds logic to exclude such clang types in the serialization
  process.

rdar://131321096&141786724