Changes:
- Rename ObjectReferenceKnowledgs::object_must_be_data_ref to
  reference_kind, introduce an enum to describe it.
- In both compilers, remove the dynamic check whether the object is an
  array/struct. This is known statically. Instead, if we are checking
  for a function, just check for rtt equality and exit.
- Remove is_data_ref_type(), replace it in the compilers with calls to
  has_signature().
- Restructure AllocateSubRtt() to handle function rtts properly.
- Add a couple execution tests.

Bug: v8:7748
Change-Id: I46fbbfe2f2a7d29b583de0d536d71c534b98322f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2661460Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72477}