Sema: Recognize non-identifier type qualifiers in enum element patterns and type expressions

[AnthonyLatsis]

Recognize non-identifier type qualifiers

• when resolving an enum element pattern. For example, the following switch statements were not considered exhaustive because the parsed expressions resolved to expression patterns:

  enum E { case a }
  let e: E
  switch e {
  case [E].Element.a: break
  } 
  

  switch Int?.none {
  case Int?.none:  break
  case Int?.some(_): break
  }
  

• in type expressions. Note that simple type expressions, like [X].Element.a, already compiled fine at the time I started working on the associated issue, but were given a suboptimal representation.

Resolves https://github.com/swiftlang/swift/issues/80632

[AnthonyLatsis]

@swift-ci please smoke test macOS

[AnthonyLatsis]

@xedin ping