Pre-share session keys when opening a room

As a user I would like to speedup sending a message (pre-share session keys when opening a room), so when typing/sending a message (in most cases) session keys are already shared and setup.

**GIVEN** session keys are not shared

**WHEN** I open a room

**THEN** session keys are shared before I start typing

### To test:

A message can also be sent from a notification (quick reply), i.e. without viewing the room timeline. This also has to be tested after any change on this part.