The register allocator sometimes fails if a parameter node appears
twice. This seems to be an issue in the register allocator rather than
a global assumption of Turbofan. This CL ensures duplication does not
happen in wasm code until the issue is resolved.

Changes:
- Cache parameter nodes in wasm-compiler.
- Use Dead() over Parameter() as placeholder in lowering stages.

Change-Id: I7afb5de45dd169819309fea3d3c1a7cfe68af62c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2756529
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73427}