Optimized code that is marked for deoptimization is not considered
'attached' or 'available', but we still want to discard it prior to
serialization. Change JSFunction::CanDiscardCompiled to explicitly
check for this case.

Bug: v8:10881, v8:10869
Change-Id: Id573c21e331afdae28be4ab434d522249d1ac9be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2409275
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69868}