This is in preparation for baseline code flushing. After a deopt we
choose to execute baseline or bytecode based on whether
SharedFunctionInfo has any baseline code. With baseline code flushing,
it is possible that baseline code is flushed after this point and before
we start executing the unoptimized code (for ex: materializing objects).
To handle such situations this CL updates the BaselineEnterAt* builtins
to check for baseline code and restart either at baseline / bytecode.

Bug: v8:11947
Change-Id: I2084e38196c882f802d1186ff8c9ab881a35b16b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3030711
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75783}