This bitset is used to quickly find the set of used / free registers,
and it should always be consistent with the information in the
{RegisterState}.
This CL adds a little validation after the register allocation of each
instruction.
This should help fuzzers to catch inconsistencies earlier.

R=thibaudm@chromium.org

Bug: v8:12330
Change-Id: Ia8da9708e982726d72d156f5bca04213a3f03b7f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3341520Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78398}