This adds a menu action to undecryptable events to request encryption keys from other devices.

Type: add

Requires: https://iron.lily-is.land/D345 https://iron.lily-is.land/D348

Open two sessions A and B.
Open a session C of the same user as B from another client that supports key sharing. Keep C online.
From A, set B to Blocked. Send an encrypted message from A to B.
Check that you cannot decrypt the event in B.
In B, set C to Verified. In C, set B to Verified.
In B, click on "Request encryption key" in the menu.
Check you can now decrypt the message.