If new Liftoff code is generated but we already have either Liftoff or
TurboFan code, we still want to install and use the new Liftoff code if
we are in debugging.

This logic can probably be simplified again when the "tier down to
liftoff on Debugger.enable" logic is fully implemented. I left a TODO to
revisit the logic later.

R=thibaudm@chromium.org

Bug: v8:10147
Change-Id: Ie3a6bdf1cde4f1af884edc8cf1f1b5a507283a5c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2036089
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66129}