... as a result of merging RelocInfo::target_object() with
RelocInfo::target_object_no_host(PtrComprCageBase),
where the cage base is used for accessing compressed embedded pointers.

There are two reasons for this change:
1) the parameterless version used to compute the cage base value from
   the host Code object, however, when external code space is enabled
   such a base value will not work for non-Code objects, since they
   require different cage base for decompressing,
2) when external code space is enabled, there must be no need to embed
   compressed Code objects at all because CodeDataContainers must be
   used instead.

In addition this CL introduces DCHECKs to enforce (2).

Bug: v8:11880
Change-Id: I5b504f91dea87c2bcaa1165d2dbfaada70cba7be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3211998Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77361}