[FLEDGE] Add restrictions to allSlotsRequestedSizes.

In particular, when both it and requestedSize are set, require
one of the sizes to match the requestedSize. Also don't allow it to be
empty, though it's valid for it not to be set.

This also means that empty lists aren't allowed.

Bug: 1506238
Change-Id: I34d81c1e478f25a02fa3ad327048d6ab19e3ac8d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5089667
Reviewed-by: Russ Hamilton <behamilton@google.com>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1235254}