There is some code common to both wide and extra wide that we are
able to hoist up since they do not affect the flags after testing
to see which version to use.

Port of https://chromium-review.googlesource.com/c/v8/v8/+/1826725

Bug: v8:9771
Change-Id: I2e40a16b784a9666df4cc5ac3ec7e8c8df5fd146
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1847358Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64184}