... and move methods that use XXX::cast() there.
This will untangle the include cycle that'll happen in a follow-up CLs.

Bug: v8:11880
Change-Id: Iba46bc9b0e0df9530197f57d0469456eb9006e66
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3164456Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76932}