swift234

Extend callee diagnosis to complex args including generics, e.g. (Void) -> T

Correctly determine callee closeness for func/ops that include generics
as part of more complicated parameters, i.e. tuple or closure args
containing generics as elements or args/results. Still only handling
single archetypes.

Also added code to check generic substitutions already made in the callee
parameters, which further helps diagnosis.