- Simplify code

- ShowChanged is only raised from presence module
- Client raises for all connection states SimpleClientState
- Simplify helper methods for getting show and show string

Modules use the state-changed signal to correctly handle connection loss

The field can not be set to an invalid value, but we need the signal
which validate generates to let users know that the form changed

Without focus keybindings like CTRL + C do not work anymore
Remove the selection on losing foucs so users know that they lost focus

With the overlay the unread counter was often not visible anymore

Fixes #10751