- Adds an AlignedSlotAllocator class and tests, to unify slot
  allocation. This attempts to use alignment holes for smaller
  values.
- Reworks Frame to use the new allocator for stack slots.
- Reworks LinkageAllocator to use the new allocator for stack
  slots and for ARMv7 FP register aliasing.
- Fixes the RegisterAllocator to align spill slots.
- Fixes InstructionSelector to align spill slots.

Bug: v8:9198

Change-Id: Ida148db428be89ef95de748ec5fc0e7b0358f523
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2512840
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71644}