swift234

Further improvement of diagnoses on args to generic functions

If the mismatched argument is on an archetype param, check to see
whether the argument conforms to all of the protocols on the archetype,
using a specific does-not-conform diagnosis if one or more protocols
fail.

Also added another closeness class
`CC_GenericNonsubstitutableMismatch`, which happens when more than one
argument is a mismatch, but all the failing arguments are of the same
type and mismatch only because of substitutability. This closeness is
farther away than normal `CC_ArgumentMismatch` so that if we note
expected matches, we’ll prefer non-generic matches. But if this is the
result, we can still produce the specific conforms-to-protocol
diagnosis (since, in a sense, it’s only one type of argument that is
wrong even though it is multiple arguments).