This makes sure that a tier-up from Ignition to TurboFan (or any other
code publishing) preserves redirections to the Interpreter. Currently an
interpreted function never switches back to compiled.

R=titzer@chromium.org
TEST=mjsunit/wasm/interpreter-mixed
BUG=v8:7921,v8:8018

Change-Id: Ifca479953509708c998c11cc00b481c232678e00
Reviewed-on: https://chromium-review.googlesource.com/1179661
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55195}