Includes mmctl into the mono-repo (#23091)

* Includes mmctl into the mono-repo

* Update to use the new public module paths

* Adds docs check to the mmctl CI

* Fix public utils import path

* Tidy up modules

* Fix linter

* Update CI tasks to use the new file structure

* Update CI references

server/cmd/mmctl/mocks/copyright.txt

@@ -0,0 +1,2 @@
+Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+See LICENSE.txt for license information.