swift234

SIL: Split up AbstractionPattern::isOpaque() into two predicates

- isTypeParameter() -- check if this is an archetype or dependent
  interface type.

- requiresClass() -- check if this is a class-constrained type
  parameter.

The old isOpaque() check has been replaced by
(isTypeParameter() && !requiresClass(moduleDecl)).

This allows us to pass the ModuleDecl on down to
GenericSignature::requiresClass(), enabling the use of
interface types in abstraction patterns.

NFC for now.