[CSSimplify] Avoid resolving extraneous (trailing) closures
If a (trailing) closure is determined to be an extraneous argument
for one of the overload choices it needs to be marked as hole as
eagerly as possible and prevented from being resolved because
otherwise it's going to be disconnected from the rest of the
constraint system and resolution might not be able to find all of
the referenced variables. This could result either in crashes
or superfluous diagnostics.
Resolves: rdar://141012049
