Move mautrix telegram and whatsapp into separate roles

The goal is to move each bridge into its own separate role.
This commit starts off the work on this with 2 bridges:
- mautrix-telegram
- mautrix-whatsapp

Each bridge's role (including these 2) is meant to:

- depend only on the matrix-base role

- integrate nicely with the matrix-synapse role (if available)

- integrate nicely with the matrix-nginx-proxy role (if available and if
required). mautrix-telegram bridge benefits from integrating with
it.

- not break if matrix-synapse or matrix-nginx-proxy are not used at all

This has been provoked by #174 (Github Issue).

roles/matrix-bridge-mautrix-telegram/tasks/main.yml

@@ -0,0 +1,21 @@
+- import_tasks: "{{ role_path }}/tasks/init.yml"
+  tags:
+    - always
+
+- import_tasks: "{{ role_path }}/tasks/validate_config.yml"
+  when: "run_setup and matrix_mautrix_telegram_enabled"
+  tags:
+    - setup-all
+    - setup-mautrix-telegram
+
+- import_tasks: "{{ role_path }}/tasks/setup-install.yml"
+  when: "run_setup and matrix_mautrix_telegram_enabled"
+  tags:
+    - setup-all
+    - setup-mautrix-telegram
+
+- import_tasks: "{{ role_path }}/tasks/setup-uninstall.yml"
+  when: "run_setup and not matrix_mautrix_telegram_enabled"
+  tags:
+    - setup-all
+    - setup-mautrix-telegram