Return the raw Object* when accessing the constant pool of bytecode
with the bytecode array accessor, to avoid needing an isolate there.
If the returned value needs to be a handle, we create the handle
later.

Bug: v8:7786
Change-Id: Ifeac2a06f0383230bf7e9bfc1b751d9750ecfb51
Reviewed-on: https://chromium-review.googlesource.com/1102334
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53784}