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-synapse/tasks/main.yml

@@ -0,0 +1,57 @@
+---
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/init.yml"
+  tags:
+    - always
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  when: run_setup | bool and matrix_synapse_enabled | bool
+  tags:
+    - setup-all
+    - setup-synapse
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/setup_synapse.yml"
+  when: run_setup | bool
+  tags:
+    - setup-all
+    - setup-synapse
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/import_media_store.yml"
+  when: run_synapse_import_media_store | bool
+  tags:
+    - import-synapse-media-store
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/register_user.yml"
+  when: run_synapse_register_user | bool and matrix_synapse_enabled | bool
+  tags:
+    - register-user
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/self_check_client_api.yml"
+  delegate_to: 127.0.0.1
+  become: false
+  when: run_self_check | bool
+  tags:
+    - self-check
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/self_check_federation_api.yml"
+  delegate_to: 127.0.0.1
+  become: false
+  when: run_self_check | bool
+  tags:
+    - self-check
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/update_user_password.yml"
+  when: run_synapse_update_user_password | bool and matrix_synapse_enabled | bool
+  tags:
+    - update-user-password
+
+- ansible.builtin.import_tasks: "{{ role_path }}/tasks/rust-synapse-compress-state/main.yml"
+  when: run_synapse_rust_synapse_compress_state | bool
+  tags:
+    - rust-synapse-compress-state
+
+- name: Mark matrix-synapse role as executed
+  ansible.builtin.set_fact:
+    matrix_synapse_role_executed: true
+  tags:
+    - always