... when external code space is enabled.

Since we are using near jump/call instruction only for [tail]calling
builtins, we can increase the code range as long as we can guarantee
that the remapped builtins are always reachable. We can do that by
remapping embedded builtins into the middle of the code range.

Bug: v8:11880, v8:12689
Change-Id: I69901634586df3c35618ea7bd5311102e4675f6c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3669107Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80810}