This reverts commit bf95ad2235.

This was a bad idea.
It's better to have people manually define the password.

Otherwise, `matrix_homeserver_generic_secret_key` changing some day in
the future would break the bot and one would have to figure out how to
reset its password manually.

Using an explicit password is more stable.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2919

* Adjust to new mrb docker versioning

* Stabilze authentication

* fix lint

* Move & document mrb password usage

* Add clean cache role

* Document clean cache

* Fix lint

* Update CHANGELOG.md

* Automate access tokens

* Improve changelog

* Make use of mrb's function to fetch API tokens

* Adjust changelog

* Use ansible.builtin.file to clear directory

* Fix typo

---------

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.