Port e893eb14

Original Commit Message:

    This adds support for having reference type values (i.e. anyref) stored
    in an exception. It is the natural combination of the reference type
    proposal and the exception handling proposal.

    Note that this also introduces support for having write barriers in
    generated WasmCode, as this is the first time we are storing references
    within generated code. Such write barriers will be needed for other uses
    of reference types (e.g. mutable global) regardless.

R=mstarzinger@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:8341
LOG=N

Change-Id: I6837a31791654ebe4171f6ecb563939beb3a66dd
Reviewed-on: https://chromium-review.googlesource.com/c/1299899Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#57009}