The unittest for {WasmCodeManager} currently disables implicit
allocations for win64 unwind info, but still deals with the implicitly
allocated jump table. With the addition of a far jump table, this logic
would get even more complex.
Thus this CL introduces a testing flag on the {WasmCodeManager} to
disable all implicit allocations, and uses that instead in the
{WasmCodeManagerTest}.

R=mstarzinger@chromium.org

Bug: v8:9477
Change-Id: I45e4bc6b9fec6d7286bf6b45f778681ae0dba746
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1725622
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63025}