swift234

Turn off typealiases in protocols.

Since there still are some holes in this feature, and I haven't had time to
fill them lately: Go back to the 2.2 behavior of treating 'typealias' keyword
in protocols as an associated type, and emit a deprecation warning.

Commented out tests specifically for typealiases in protocols for now, and
random validation tests that crash or not based on whether keyword is interpreted as associatedtype or typealias updated.