Updates the message to use the type or ValueDecl instead of this on previous 'Found this candidate' messages
Note: doees not yet change all test cases so more tests are failing
Improve Diagnostic message on overload ambiguitiy
Remove messages that say 'found this candidate' in favour of providing the type for the candidate to aid in selection when the candidates are presented in a dialogue window.
Fix more tests
With `ARCMigrate` and `arcmt-test` removed from clang in
https://github.com/llvm/llvm-project/pull/119269 and the new code
migration experience under way (see
https://github.com/swiftlang/swift-evolution/pull/2673), these options
are no longer relevant nor known to be in use. They were introduced
long ago to support fix-it application in Xcode.
For now, turn them into a no-op and emit a obsoletion warning.
Some invalid specializations were previously allowed by the compiler
and we found some existing code that used that (albeit invalid) syntax,
so we need to stage that error as a warning until Swift 6 language mode
to avoid source compatibility break.
Resolves: rdar://134740240
