Reland "[OpenMPOpt] ICV Tracking"

This reverts commit 1d542f0c.

`recollectUses()` is added to prevent looking at dead uses after
Attributor run.

This is the first and most basic ICV Tracking implementation. For this
first version, we only support deduplication within the same BB.

Reviewers: jdoerfert, JonChesterfield, hamax97, jhuber6, uenoku,
baziotis, lebedev.ri

Differential Revision: https://reviews.llvm.org/D81788