[Attributor] Cache query results for isPotentiallyReachable in AAReachability

Summary:
This is the next patch of [[ https://reviews.llvm.org/D76210 | D76210 ]].
This patch made a map in `InformationCache` for caching results.

Reviewers: jdoerfert, sstefan1, uenoku, homerdin, baziotis

Reviewed By: jdoerfert

Subscribers: hiraditya, uenoku, kuter, bbn, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83246