swift234

Simplify handling of metatypes in devirtualization.

Make the devirtualization functions take the actual type we're
devirtualizing (or speculatively devirutalizing) to, in order to
simplify the handling of metatypes. Remove the ClassDecl parameter from
these functions since it can always be derived from this type.

These changes set things up for more forthcoming improvements to
metatype handling.

As part of this I've simplified the function that determines if a member
is known to be 'final'. My expectation is that this can be further
simplified by removing the type parameter as part of other improvements
to metatype handling.

Swift SVN r26165