When pointer compression is enabled the [u]intptr_t and double fields are
only kTaggedSize aligned so in order to avoid undefined behavior in C++ code
we have to access these values in an unaligned pointer friendly way although
both x64 and arm64 architectures (where pointer compression is supported)
allow unaligned access.

These changes will be removed once v8:8875 is fixed and all the
kSystemPointerSize fields are properly aligned.

Bug: v8:7703
Change-Id: I4df477cbdeab806303bb4f675d52b61c06342c8e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1528996
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60321}