... when external code space is enabled.
Currently this mode is guarded by V8_REMOVE_BUILTINS_CODE_OBJECTS flag
which is set to false until Code-less builtins are supported.

Drive-by:
* remove unnecessary methods from AbstractCode,
* avoid CodeDataContainer <-> Code roundtrips when accessing writable
  state of Code objects via CodeT.

Bug: v8:11880
Change-Id: Iae3ff3b2feae68d875cbe9f82a6bb076460dd2f8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3769832
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81814}