- Infer type wrappers only from direct (declared on type) protocols
- Inferences from protocol to protocol is not allowed
- If type specifies a type wrapper attribute explicitly it has to
match the one associated with a declared protocol, otherwise the
declaration is going to be rejected as having multiple wrappers.
When compiling with allow errors, it's possible to have invalid
inherited types - both null and ErrorType.
Cleaned up the tests a little - moved the majority of
Frontend/allow-errors.swift into separate files in
Serialization/AllowErrors and use split_file.py instead of #defines.
Resolves rdar://78048470
