* 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