[DATABASE] Some query improvements

Make common_sql_weight employ standard SQL functions for the timestamp
difference in seconds.
Also replace UTC_TIMESTAMP in the MariaDB-specific part with CURRENT_TIMESTAMP
as it is the only occurence and GNU social sets UTC as a default timezone.

In a delete_orphan_files.php script simplify the main query considerably.

In clean_profiles.php stop using COUNT as if it is ANY, that is unnecessary
punishment for the database. Instead implement the anti-join with a
left outer join.

In Autocomplete and Activitypub_profile use joins instead of a WHERE OR
anti-pattern for the semi-joins.

In lib/ui/galleryaction.php replace a CROSS JOIN with an INNER JOIN.

In actions/sup.php remove a redundant subquery: WHERE is applied before
grouping either way.

plugins/Nodeinfo/actions/nodeinfo_2_0.php

@@ -338,7 +338,8 @@ class Nodeinfo_2_0Action extends Action
                 UNION ALL
                 SELECT id FROM {$userTable} WHERE {$userTable}.created >= CURRENT_DATE - INTERVAL '{$days}' DAY
               ) AS source
-              WHERE profile_id NOT IN (SELECT profile_id FROM profile_role WHERE role = 'silenced')
+              LEFT JOIN profile_role USING (profile_id)
+              WHERE profile_role.profile_id IS NULL OR profile_role.role <> 'silenced';
             END;
 
         $activeUsersCount = new DB_DataObject();