* Add matrix_bridges_msc4190_enabled flag for using msc4190 on supported mautrix bridges.
* Apply to_json to msc4190 in mautrix configs
* Add | to_json to mautrix bridge registration io.element.msc4190.
* require matrix_synapse_experimental_features_msc3202_device_masquerading_enabled for matrix_bridges_msc4190_enabled
* Also add msc4190 support for mautrix-telegram
This:
- brings consistency - no more mixing `_name_prefix` and `_registry_prefix`
- adds extensibility - a future patch will allow reconfiguring all registry prefixes for all roles in the playbook
We still have `_docker_` vs `_container_` inconsistencies.
These may be worked on later.
