This removes dead and obsolete support for batch-saved register from the
safepoint table. We no longer spill the entire register window (either
double or general-purpose) from optimized code. All spills happen as
part of the normal spill-slots on the stack by now.

R=clemensh@chromium.org,jarin@chromium.org
BUG=v8:9183

Change-Id: I5a2be7a543fa3e44d71ab1a35c722da0d458765c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627531
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61815}