[Attributor] [WIP] Track AA dependency using dependency graph

Summary: This patch added dependency graph to the attributor so that we can dump the dependencies between AAs more easily. We can also apply general graph algorithms to the graph, making it easier for us to create deep wrappers.

Reviewers: jdoerfert, sstefan1, uenoku, homerdin, baziotis

Reviewed By: jdoerfert

Subscribers: jfb, okura, mgrang, kuter, lebedev.ri, hiraditya, uenoku, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78861