Alert Improvements by Xon 2.12.2

• Fix edge case where clicking 'mark read' on an alert or the 'all' alerts button would miss updating alerts
• Add confirmation prompt when clicking "mark read" for marking alerts as read.
• Add per-user "Prompt on bulk mark read" option. Controlled by the global "Mark-read prompt opt-out" option.

Require StandardLib v1.21.0+
XF2.3 support
Recommend a minimum of XF2.3.2, as otherwise alert totals do not update as expected

Add "Use stock UI for marking alerts as read" style property (default disabled)

• When the user's alert count is non-zero, the alert-popup is forced to fetch unread alerts first, and if no unread alerts are discovered this indicates the user's alert count is out-of-sync and needs to be reset.

• Add explain text to the "Use custom" value for "Alerting Preferences" per-user option
• Add "[Alert Improvements] Can customize advanced alert preferences" permission to control is a user can change the following per-user preferences: "Alerts page options"/"Alert pop-up options"/"Alerts summarize threshold"
  Permission granted to Registered user group by default

• Fix incorrect phrase for default alert type in admincp
• Fix new alert types could be opted out by default instead of opt-in
• Fix user's alert preferences may not save with some configurations
• On alert opt-out list; only render "reset" checkbox for non-default values

• Fix setting "Alerts page skips summarizing" in "User Registration" to false wasn't applied to new accounts

• Fixes for grouped/summarized alerts
• Group by newest alert not oldest when computing alert summary data
• When gluing together per-content type reaction summary, use ", " not just whitespace.

• Fix unsetting "Pop-up auto-read" for some XF stock alerts would fail

• Fix "getSvAlertPref(): Return value must be of type array, null returned" when adding a user via the admincp
• Force a consistent mysql locking ordering of affected user records when a user receives a reaction