This refactors ConvertToRelativeIndex into a clamping version and a
version that takes OOB labels for the upcoming implementation of
Array#with and TypedArray#with.

Also gets rid of the the "to" in the name, because these macros are
actually converting _from_ a relative index to an absolute one, not
the other way around.

Bug: v8:12764
Change-Id: I8bf1c16ce73008164acbd6b849f4259fb9315274
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3669655Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80786}