swift234

Extend callee diagnoses to non-conforming complex args including generics.

Previously, type checking arguments worked fine if the entire arg was
UnresolvedType, but if the type just contained UnresolvedType, the
constraint system always failed via explicitly constraining to
unresolved.

Now in TypeCheckConstraints, if the solution allows for free variables
that are UnresolvedType, then also convert any incoming UnresolvedTypes
into variables. At worst, in the solution these just get converted back
into the same Unresolved that they started with.

This change allows for incorrect tuple/function type possibilities to
make it back out to CSDiag, where they can be more precisely diagnosed
with callee info. The rest of the changes are to correctly figure
out the failure info when evaluating more types of Types.

New diagnosis for a partial part of an arg type not confroming. Tests
added for that. Expected errors changed in several places where we
now get real types in the diagnosis instead of '(_)' unresolved.