[Diagnostics] Handle CoerceExpr conversion failure in contextual mismatch

[LucianoPAlmeida]

While working in #27895, more specifically in 82529a6 I note that the cannot convert diagnostic for expr Double(1) as Double as String is being emitted via fix but still going re-typechecking passing through CSDiag. Note that actually when tried to put a if (Options.contains(ConstraintSystemFlags::SubExpressionDiagnostics)) in applySolutionFixes.
So this PR is to handle coercion conversion error early on repairFailures and avoid this.
This also handles the TODO diagnostic in test/type/subclass_composition.swift.

cc @xedin @hborla :))

[xedin]

@LucianoPAlmeida Thank you, I'll take a look on Monday! Meanwhile, can check you check how much fails if you remove FailureDiagnosis::visitCoerceExpr?

[LucianoPAlmeida]

Sure @xedin, will check as soon as possible 👍

[LucianoPAlmeida]

@xedin removing FailureDiagnosis::visitCoerceExpr only fails 5 tests:

Failing Tests (5):
    Swift(macosx-x86_64) :: Generics/conditional_conformances_literals.swift
    Swift(macosx-x86_64) :: Sema/suppress-argument-labels-in-types.swift
    Swift(macosx-x86_64) :: expr/cast/metatype_casts.swift
    Swift(macosx-x86_64) :: expr/cast/optional.swift
    Swift(macosx-x86_64) :: type/subclass_composition_objc.swift

  Expected Passes    : 4950
  Expected Failures  : 23
  Unsupported Tests  : 122
  Unexpected Failures: 5

I do remove some obsolete code from it, but can try to figure out the missing cases in a follow-up PR so it can be removed for good \o/
Most of them are coercions involving metatypes, so probably handle a complex locator should fix most ... other cases I have to look and see why they are failing :)

[xedin]

@LucianoPAlmeida That would be great!

[xedin]

Looks great! I have left a minor naming suggesting inline.

[xedin]

@swift-ci please smoke test

[LucianoPAlmeida]

@xedin Thanks, I'm starting to work on handle the other failures, maybe we'll have something soon :)

[xedin]

Sounds good, thank you!