swift234

Use the known type parameters to determine static offsets to stored
properties of classes with generic layouts.

Previously we were falling back on accessing them via the field
offset vector even when we knew everything about the type.

As a minor benefit, this allows RemoteAST to also determine offsets
for members of classes with generic layout.

Half of the test changes are IR type-name uniquing; I'm going to
explore mangling these with the full type where possible.