Mautrix

* *(crypto)* Fixed bug in crypto store migration when using outbound sessions with max age higher than usual.

* *(crypto)* Updated crypto store schema to match mautrix-go.
* *(types)* Fixed `set_thread_parent` adding reply fallbacks to the message body.

* *(bridge, crypto)* Fixed key sharing trust checker not resolving cross-signing signatures when minimum trust level is set to cross-signed.

* *(crypto)* Added cache checks to prevent invalidating group session when the server sends a duplicate member event in /sync.
* *(util.proxy)* Fixed `min_wait_seconds` behavior and added `max_wait_seconds` and `multiply_wait_seconds` to `proxy_with_retry`.

* *(util.proxy)* Added utility for dynamic proxies (from mautrix-instagram/facebook).
* *(types)* Added default value for `upload_size` in `MediaRepoConfig` as the field is optional in the spec.
* *(bridge)* Changed ghost invite handling to only process one per room at a time (thanks to maltee1 in 132).

* *(types)* Changed `set_thread_parent` to inherit the existing thread parent if a `MessageEvent` is passed, as starting threads from a message in a thread is not allowed.
* *(util.background_task)* Added new utility for creating background tasks safely, by ensuring that the task is not garbage collected before finishing and logging uncaught exceptions immediately.