[Analysis] Remove DA & LegacyDA

UniformityAnalysis offers all of the same features and much more, there is no reason left to use the legacy DAs.
See RFC: https://discourse.llvm.org/t/rfc-deprecate-divergenceanalysis-legacydivergenceanalysis/69538

- Remove LegacyDivergenceAnalysis.h/.cpp
- Remove DivergenceAnalysis.h/.cpp + Unit tests
- Remove SyncDependenceAnalysis - it was not a real registered analysis and was only used by DAs
- Remove/adjust references to the passes in the docs where applicable
- Remove TTI hook associated with those passes.
- Move tests to UniformityAnalysis folder.
  - Remove RUN lines for the DA, leave only the UA ones.
- Some tests had to be adjusted/removed depending on how they used the legacy DAs.

Reviewed By: foad, sameerds

Differential Revision: https://reviews.llvm.org/D148116