The kCallOnHeapBuiltin name has gotten very confusing now
that builtins are actually off the heap (and the generated code will
directly call off-heap).

Bug: v8:7777
Change-Id: Ie14069eee2fc11ef9aec64868c50832f6138ae8f
Reviewed-on: https://chromium-review.googlesource.com/c/1379883Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58291}