The most common case is still one of the unconditionally supported (MVP)
types. Hence avoid the switch and the flags / CPU features lookup in the
hot function, and offload that to a rarely called function. The fast
path is now just a bit check via an EnumSet.

R=thibaudm@chromium.org

Change-Id: I0cee94640bcc0e5e0fa636e23eb0ba5460d8b8fd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2778271Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73611}