Add an unboxing double field load node, and fix a couple of locations
where it might be used enough to pass tests.

Bug: v8:7700
Change-Id: Ic134484e87a4fa363cbd8a3de667ac8e8116d502
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3610623Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80221}