Changes:
- Remove an obsolete TODO from wasm-module-builder.
- Replace CHECK with gTest's EXPECT in unittests.
- Remove setting of --experimental-wasm-liftoff-extern-ref in wasm-gc.
- Test test-gc/JSAccess with Liftoff.
- Remove useless #undef's from module-decoder-unittest.

Change-Id: I11b4a3dde9683cc9c7d1eb89b1a63e1859505aad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2659063
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72455}