This is a reland of commit 9b0d5cb1

The newly added check does not allow comparisons with stale or
invalid pointers because attempt to access the page header might
crash.

Original change's description:
> [ext-code-space] Fix Code vs non-Code comparisons
>
> 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/+/3838172
> Reviewed-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}

Bug: v8:11880
Change-Id: Iab3c8fe49cb954b2dc9171b3fc4b189e84763e73
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3842932Reviewed-by: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82624}