This PR fixes things so that:
* when the `BottomPane` is in the `StatusIndicator` state, the border
should be dim
* when the `BottomPane` does not have input focus, the border should be
dim
To make it easier to enforce this invariant, this PR introduces
`BottomPane::set_state()` that will:
* update `self.state`
* call `update_border_for_input_focus()`
* request a repaint
This should make it easier to enforce other updates for state changes
going forward.
a1f51bf91b