LdaLookupGlobal/ContextSlot loop over parent contexts to check for
context extensions. If there aren't any, they can do a fast
context/global load, otherwise they have to call a runtime slow path.

The bytecode graph builder didn't build a slow path in the case where no
context extensions are possible, by depth == 0 or static scope info
information that there are no possible context extensions. However, this
information is already known to the interpreter, so that should already
elide the lookup in these cases. So, get rid of the slow path being
optional in TurboFan, and consider such cases bytecode generation bugs.

Change-Id: Ib69f90e51b0f783306824fed56911d039f7e134e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3872277
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82972}