When external code space is enabled comparing Code and non-Code objects
by looking at compressed values is not always correct. Such an approach
works only for comparing Code vs Code objects or non-Code vs non-Code
objects.

This CL instroduces SLOW_DCHECK into Object comparison operators to
ensure that such a comparison is allowed. Also, this CL instroduces
an Object::SafeEquals() method which compares uncompressed values
and thus is safe to be used for comparing Code with non-Code objects.

Bug: v8:11880
Change-Id: I7ccf1f90f927beb2bb9f45efb303e902b1838d02
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3838172Reviewed-by: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82611}