This CL reinstates the old pow implementation which calls out to the
system implementation of pow.

Bug: v8:9622
Change-Id: I3df997888ced3fb8b5bd4b810098e967649aaa55
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1774898Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66303}