Direct share, hide media, extensions, and more

* Fix direct shares on Android 12+
* Option to hide media from gallery
* Do not re-notify dismissed notifications
* Experimental extensions support based on WebXDC
* Experimental XEP-0227 export support
* Links for more URI schemes
* Option to disable custom tab UI for links
* Add warnings to backup process
* Unify camera/camcorder/picture as "choose media"
* Try harder to send attachments in order
* Better reaction notifications
* Add account from drawer
* Restore backup from add account
* Option to block or allow call ring from strangers
* Fix sending custom reaction we don't have the image downloaded for yet
* Fix for amazon.{ca, com} link previews

Artifacts