This introduces {GetWasmFunctionOffset} to replace the above method,
since calculating offsets into the wire bytes is independent of the
concrete module object and hence only needs the shared decoded module.

R=clemensh@chromium.org
BUG=v8:6847

Change-Id: I6818de4589e26dd8f69dfb71d15bbca127c7ee3e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1809368Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63862}