To avoid external-reference.cc having to depend on code-assembler.h,
this moves ObjectType and CheckObjectType into a separate
objects/object-type.h/.cc.

Bug: v8:11879
Change-Id: Ia086b37f72c330eefef2ce4d35cdf31d2a0ebe62
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3009220
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75599}