Since we always call the out-of-line Prologue, we can preload the
accumulator in there with undefined instead of having to emit an
undefined load in every Sparkplug code header.

Change-Id: Ie0385316b0ee8bf96cd0069cda0496d05a4fb1eb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2933144Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74919}