* appservice: add and use matrix_homeserver_* vars

* appservice: use the new vars

* Apply suggestions from code review

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

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

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

Update group_vars/matrix_servers

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

Remove old data migration tasks

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

Update roles/matrix-bridge-mautrix-discord/tasks/validate_config.yml

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

Redo bridge permissions