The reference stack was set by the scope, and reset when leaving the
scope, in order to avoid leaking objects via cycles in the reference
tree, involving global handles which are considered strong roots.
Since the interpreter cannot call out to JS any more, we cannot create
such cycles any more. Hence, the ReferenceStackScope is removed, and the
FixedArray for the reference stack is allocated as a global handle
instead.

This will unblock removing the WasmDebugInfo object, which was used by
the ReferenceStackScope before this CL.

R=ahaas@chromium.org

Bug: v8:10389
Change-Id: I2e3c6a03750846679eecd9e6a07042db962aad9c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2235542Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68257}