BranchElimination and CsaLoadElimination interracted badly and created
quadratic behavior when run together. This happened when
CsaLoadElimination kept updating arguments of a Merge, and
BranchElimination kept going through all of them to find the common
prefix of all path conditions. Therefore, we separate BranchElimination
and CsaLoadElimination in the csa and wasm optimization pipelines.

Additional changes:
- Split WasmOptimizationPhase from CsaOptimizationPhase.
- Remove now-redundant argument from CsaOptimizationPhase::Run.
- Fine-grain how statistics are measured in the wasm pipeline.

Change-Id: Id166f4f7d1ea69a1a7b7ca108af4ffedbcda8abb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2912779
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74779}