[NewOptimizer] Port #26826 to new optimizer (#26981)
* fix InferenceResult cache lookup for new optimizer
* utilize cached vararg type info in new inlining pass
* fix test to work with new optimizer
* fix predicate for exploiting cached varargs type info
* atypes no longer needs to be modified to match cached types
* don't require varargs to be in last position to exploit cached type info
* restore missing isva boolean
