[clang] [ObjC] Emit number, array, and dictionary literals as constants (PR #185130)

[John McCall via cfe-commits]

rjmccall wrote:

The Foundation folks at Apple seem to be in agreement that the right path forward is to keep this enabled by default and just alert people that `-isEqualToValue:` can have surprising and not totally reliable behavior. We should just make sure the behavior change is described thoroughly in a release note.

https://github.com/llvm/llvm-project/pull/185130