Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/scripts/replica-lag-set.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+stmt="STOP SLAVE SQL_THREAD FOR CHANNEL '';CHANGE MASTER TO MASTER_DELAY = $1;START SLAVE SQL_THREAD FOR CHANNEL '';SHOW SLAVE STATUS\G;"
+docker exec mattermost-mysql-read-replica sh -c "export MYSQL_PWD=mostest; mysql -u root -e \"$stmt\"" | grep SQL_Delay