[AMDGPU] Use UniformityAnalysis in AtomicOptimizer

Adds & uses a new `isDivergentUse` API in UA.
UniformityAnalysis now requires CycleInfo as well as the new temporal divergence API can query it.

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Original patch that adds `isDivergentUse` by @sameerds

The user of a temporally divergent value is marked as divergent in the
uniformity analysis. But the same user may also have been marked divergent for
other reasons, thus losing this information about temporal divergence. But some
clients need to specificly check for temporal divergence. This change restores
such an API, that already existed in DivergenceAnalysis.

Reviewed By: sameerds, foad

Differential Revision: https://reviews.llvm.org/D146018