This adds support for handling reference types when loading/storing
globals. Support for imported mutable globals is still missing and will
be done in a follow-up change.

R=clemensh@chromium.org
TEST=mjsunit/wasm/exceptions-global-interpreter
BUG=v8:8091,v8:7581

Change-Id: I0d14919b1ce7f49c4a0541e3d6a99ee203cfb311
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1558086
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60695}