[wasm-gc] Remove obsolete RTT statements from function body decoder

This change removes:
- struct.new_with_rtt
- struct.new_default_with_rtt
- array.new_fixed
- array.new_data
- array.new_with_rtt
- array.new_default_with_rtt
- ref.test
- ref.cast
- br_on_cast
- br_on_cast_fail
- rtt.canon

Bug: v8:7748
Change-Id: Iadf73c294904ec20cefe1053a2969aa1dbb91a39
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3779689
Auto-Submit: Matthias Liedtke <mliedtke@google.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Matthias Liedtke <mliedtke@google.com>
Cr-Commit-Position: refs/heads/main@{#81892}