26148: Makefile,pkg/ui: fix compilation of JS CCL protobufs r=couchand,mberhault a=benesch

Main commit message reproduced below, but there are two smaller commits as well.

---

PR #26040 introduced a dependency on CCL protobufs in the UI. The build
changes in that PR were slightly buggy; specifically, any protobuf that
was depended upon by both an OSS and CCL protobuf would be included in
the JavaScript bundle twice. This sort of double-inclusion causes subtle
problems, like the deepEqual in a unit test that suddenly started
failing [0].

To ensure only one copy of each protobuf is included, have the OSS and
CCL UI builds depend upon completely independent protobuf DLLs. The OSS
protobuf DLL includes only OSS protobufs, of course, while the CCL
protobuf DLL includes both the OSS and CCL protobufs. The protobuf
compiler, pbjs, takes care of including each dependent protobuf exactly
once.

To avoid creating a webpack configuration for each distribution and
distribution (i.e., webpack.protos.ccl.js and webpack.protos.oss.js),
use webpack's support for parameterized configs. For consistency,
collapse webpack.oss.js and webpack.ccl.js into a parameterized config
in webpack.app.js.

Additionally, deduplicate the Make rules that compile the CCL JavaScript
and TypeScript protobufs. The OSS and CCL rules are nearly identical, so
they can share a recipe with a little bit of Make magic.

[0]: https://github.com/cockroachdb/cockroach/pull/26040/files#diff-9c8c2f256576e5704513c79be1173f5cR452

26329: roachpb/client: remove LegacyRangeLookup and DeprecatedRangeLookupRequest r=nvanbenschoten a=nvanbenschoten

Cockroach 2.1 clusters will always support meta2 splits, so the legacy
range lookup approach is never allowable. No node in a 2.1 cluster will
send DeprecatedRangeLookupRequests either, so the code is no longer needed.

The change also removes the `DeprecatedReturnIntents` option on ScanRequests.
This option was a predecessor to the READ_UNCOMMITTED read consistency type.
It was only used in 1.1, so it no longer needs to be supported in 2.1 clusters.

26368: opt: enable distsql_union, fix some issues r=RaduBerinde a=RaduBerinde

#### opt: fix two cases of errors caused by "inner" ORDER BY

When the `ORDER BY` adds columns to the scope, we want to remove these
columns before set operations, and for subqueries.

Release note: None

#### opt: fix set operations crash during exec

When building a set operation, we use the leftScope which might have
an ordering. This ordering must be discarded (it can refer to columns
that have been removed, causing a crash when we try to execbuild the
query).

Release note: None

#### opt: split distsql_union and enable for opt

The opt version of the planner test has some distsql plan differences;
they are mostly due to the optimizer ignoring inner ORDER BY (which
the planner doesn't).

Release note: None


Co-authored-by: Nikhil Benesch <nikhil.benesch@gmail.com>
Co-authored-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>
Co-authored-by: Radu Berinde <radu@cockroachlabs.com>

In cockroachdb#26148 the make watch task was missed.  This updates that to run with
the new webpack config.

Release note: None

26371: build, ui: fix make watch r=couchand a=couchand

In #26148 the make watch task was missed.  This updates that to run with
the new webpack config.

Release note: None

Co-authored-by: Andrew Couch <andrew@cockroachlabs.com>