Add-ons Alert Improvements by Xon 2.12.2

• Reduce possibility of deadlocks when pruning alert cleanup table
• Fix summary alert pagination

• Add CLI command "xf-rebuild:sv-alert-totals" to expose rebuilding alert totals job
• Avoid updating alerts which are condinates to be pruned, this should reduce the possibility of the alerts cleanup tasks generating deadlocks

• Fix "Call to a member function keys() on array"
• Fix that very old alerts could be shown in the alerts pop-up
• Increase thickness of border between unread and read alerts
• Force unread alerts to be preferred when fetching alerts in the alerts pop-up