Now ChangeLowering is only concerned with lowering memory access and
allocation operations, and all changes are consistently lowered during
the effect/control linearization pass. The next step is to move the
left over lowerings to a pass dedicated to eliminate redundant loads and
stores, eliminate write barriers, fold and inline allocations.

Drive-by-fix: Rename ChangeBitToBool to ChangeBitToTagged,
ChangeBoolToBit to ChangeTaggedToBit, and ChangeInt31ToTagged to
ChangeInt31ToTaggedSigned for consistency.

CQ_INCLUDE_TRYBOTS=tryserver.v8:v8_linux64_tsan_rel

Committed: https://crrev.com/ceca5ae308bddda166651c654f96d71d74f617d0
Cr-Commit-Position: refs/heads/master@{#35924}

Review-Url: https://codereview.chromium.org/1941673002
Cr-Commit-Position: refs/heads/master@{#35929}