When reading the FixedDoubleArray value and representation, we are
reading the same value but bitcasting it diffrently. In this vein, we
can read it only once and ask whether it is the hole or not.

Bug: v8:7790
Change-Id: I0d7b29ce037b9abb55c5a1332c7e6d06887905e1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2428587Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70119}