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-base/tasks/main.yml

@@ -0,0 +1,37 @@
+---
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/sanity_check.yml"
+  tags:
+    - always
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/clean_up_old_files.yml"
+  when: run_setup | bool
+  tags:
+    - setup-all
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/server_base/setup.yml"
+  when: run_setup | bool
+  tags:
+    - setup-all
+
+# This needs to always run, because it populates `matrix_user_uid` and `matrix_user_gid`,
+# which are required by many other roles.
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/setup_matrix_user.yml"
+  when: run_setup | bool
+  tags:
+    - always
+    - setup-system-user
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/setup_matrix_base.yml"
+  when: run_setup | bool
+  tags:
+    - setup-all
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/setup_well_known.yml"
+  when: run_setup | bool
+  tags:
+    - setup-all
+    - setup-ma1sd
+    - setup-synapse
+    - setup-dendrite
+    - setup-nginx-proxy