This implements arithmetic operations on f64, as well as
conditional set for the arm32 port of Liftoff.

Bug: v8:6600
Change-Id: Ia060652e5292ed94da8a0ba656bddbcc13d9f610
Reviewed-on: https://chromium-review.googlesource.com/c/1348349
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57841}