Currently, we are flushing current allocation group state on loop entry.
With this CL, we only flush the state for loops that can allocate.
Non-allocating loop will preserve the state. This enables more
optimization opportunities for write barrier elimination and
allocation folding.

Unforutnately, the optimization will only trigger for
compiler-introduced loops - user loops always contain stack check
(which can allocate).

Bug: v8:8984
Change-Id: I5a47accec92455f4aabb0129800773596712029a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1541043Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60501}