swift234

AST: Use GenericEnvironment in ArchetypeBuilder::mapType{Into,OutOf}Context()

When we call the DeclContext variants of these, use the
DeclContext's GenericEnvironment instead of GenericParamList.

Also, these functions would take a resolver argument, but we
always passed in nullptr, so just remove it now.

The old GenericParamList-based versions are still there
since they're called directly from SIL. They will go away
once SILFunction::ContextGenericParams is replaced with
a GenericEnvironment.