Move roles/matrix* to roles/custom/matrix*

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.

roles/custom/matrix-bot-postmoogle/tasks/setup_uninstall.yml

@@ -0,0 +1,36 @@
+---
+
+- name: Check existence of matrix-postmoogle service
+  ansible.builtin.stat:
+    path: "{{ matrix_systemd_path }}/matrix-bot-postmoogle.service"
+  register: matrix_bot_postmoogle_service_stat
+
+- name: Ensure matrix-postmoogle is stopped
+  ansible.builtin.service:
+    name: matrix-bot-postmoogle
+    state: stopped
+    enabled: false
+    daemon_reload: true
+  register: stopping_result
+  when: "matrix_bot_postmoogle_service_stat.stat.exists | bool"
+
+- name: Ensure matrix-bot-postmoogle.service doesn't exist
+  ansible.builtin.file:
+    path: "{{ matrix_systemd_path }}/matrix-bot-postmoogle.service"
+    state: absent
+  when: "matrix_bot_postmoogle_service_stat.stat.exists | bool"
+
+- name: Ensure systemd reloaded after matrix-bot-postmoogle.service removal
+  ansible.builtin.service:
+    daemon_reload: true
+  when: "matrix_bot_postmoogle_service_stat.stat.exists | bool"
+
+- name: Ensure Matrix postmoogle paths don't exist
+  ansible.builtin.file:
+    path: "{{ matrix_bot_postmoogle_base_path }}"
+    state: absent
+
+- name: Ensure postmoogle Docker image doesn't exist
+  community.docker.docker_image:
+    name: "{{ matrix_bot_postmoogle_docker_image }}"
+    state: absent