ReplicatedPG::mark_all_unfound_lost: delete local copy if necessary

There might be a local copy for an EC pool in the DELETE case.  The replica
copies should be already handled by merge_log.

Fixes: #7439
Signed-off-by: Samuel Just <sam.just@inktank.com>
Merge remote-tracking branches 'origin/wip-sam-testing2', 'origin/wip-7942', 'origin/wip-8124', 'upstream/wip-7891', 'origin/wip-7588', 'origin/wip-8011' and 'origin/wip-7439' into wip-sam-testing