We implement two optimizations for trap conditionals for patterns that
come up in wasm-gc.
In case of a Merge followed by a trap, where the path conditions of all
branches of the Merge contain the trap condition, we lift the trap into
the branches of the Merge.
In case of a Branch whose IfTrue branch is followed by a TrapIf with the
same condition, we replace it with the trap followed by the IfFalse
branch. Symmetrically for IfFalse and TrapUnless.

Bug: v8:7748
Change-Id: I43040aebe60eab7b2230fc3130e3b8250e8b2f45
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3190109Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77181}