The macro is not needed, the same condition can also be expressed
programmatically. Its name is misleading anyway, since it has nothing to
do with the wasm64 proposal.

Drive-by: Use GraphAssembler to implement {BuildF64CopySign}.

R=jkummerow@chromium.org, tebbi@chromium.org

Bug: v8:10123, v8:10155
Change-Id: I85238172037f08bd2e4d2d4564950759524f991a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105637Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66743}