The purpose of this CL is:
- To include all the logic of this function within the bit case switch.
- To make it more clear what the probabilities for each generated
  subtype are.
- To fix bugs where anyref fell back to unsupported types in interpreter
  mode.

Bug: v8:11954
Change-Id: Ibc2d487c3fd66ec44a2a4f0eee874c8d3591be52
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3220347Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77385}