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/build/docker/prometheus-linux.yml

@@ -0,0 +1,8 @@
+global:
+  scrape_interval: 5s
+  evaluation_interval: 60s
+
+scrape_configs:
+  - job_name: 'mattermost'
+    static_configs:
+      - targets: ['172.17.0.1:8067']