[PR49761] Fix variadic arg handling in matcher

Mishandling of variadic arguments in a function call caused a crash
(runtime assert fail) in bugprone-infinite-loop tidy checker.  Fix
is to limit argument matching to the lesser of the number of variadic
params in the prototype or the number of actual args in the call.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D101108