when applicable.

This CL also renames BodyDescriptorBase helpers
  IsValidSlotImpl() -> IsValidJSObjectSlotImpl()
  IterateBodyImpl() -> IterateJSObjectBodyImpl()
to make it clear that these methods are only applicable to JSObject subclasses
and fixes SmallOrderedHashTable::BodyDescriptor which used IsValidSlotImpl().

Bug: v8:8518
Change-Id: I11565bed6ebf56c6830ac0e21f866846e65025e6
Reviewed-on: https://chromium-review.googlesource.com/c/1372068
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58170}