Soft-deopt for mono/polymorphic property accesses that don't have any
maps, and only allow zero-map feedback to be monomorphic. This makes
sure we only emit a megamorphic LoadIC builtin call if the IC was
actually megamorphic.

JSGenericLowering assumed that zero maps meant that a load site is
megamorphic. However, it can be the case that the call-site is
monomorphic or polymorphic, and the maps had died. In this case we don't
want to call the megamorphic IC builtin, as on a stub cache miss we
fallback to a normal LoadIC miss, which can record mono/polymorphic
feedback in the IC. After this, we'll enter a miss loop in the
megamorphic load builtin, and worse the LoadIC assumes that there's
something "wrong" with the feedback, so it'll keep trying to reconfigure
the handler (possibly allocating new load handlers if this is a
prototype field access).

As a drive-by, rewrite GetRelevantReceiverMaps to be an in-place
filtering of the maps rather than copying them.

Change-Id: I0c25bfa606367fa81c43223bbd56cdadb5e789ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2150586Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67152}