[ConstraintSystem] Teach `getFunctionArgApplyInfo` about `inout` expressions
Currently `getFunctionArgApplyInfo` expects a locator with `ApplyArgToParam`
element to identify location of the argument. `InOutExpr` could only be used
in argument positions but it doesn't have the same locator format as non-inout
arguments, so `getFunctionArgApplyInfo` needs to do some digging in the AST
to retrieve that information.
Resolves: rdar://75146811