Mautrix

* *(client)* Fixed dispatching room ephemeral events (i.e. typing notifications) in syncer.

* *(bridge)* Implemented appservice pinging using MSC2659.
* *(bridge)* Started reusing aiosqlite connection pool for crypto db.
* This fixes the crypto pool getting stuck if the bridge exits unexpectedly (the default pool is closed automatically at any type of exit).

* *(crypto)* Fixed bug with redacting megolm sessions when device is deleted.

* *(bridge)* Fixed backwards-compatibility with new key deletion config options.

* *(crypto)* Fixed bug in previous release which caused errors if the `max_age` of a megolm session was not known.
* *(crypto)* Changed key receiving handler to fetch encryption config from server if it's not cached locally (to find `max_age` and `max_messages` more reliably).

* *(crypto, bridge)* Added options to automatically ratchet/delete megolm sessions to minimize access to old messages.