... in an uintptr friendly way.

Drive-by-fix:
1) IsForceSlowPath() check is integrated into Cast<FastJSArray>
2) disable tests incompatible with --force-slow-path in "slow_path" variant

Bug: v8:8906, v8:4153
Change-Id: I427f117073bc295120aa52fb3fe023ee04d58302
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1899988
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64799}