Take minibuffer input asynchronously

[Piturnah]

Here we take the minibuffer input asynchronously, meaning that instead of calling take_input from within the event loop and then blocking until we have input, we instead switch to an alternative input view, providing a callback for when the input is received.

Motivation

• Will fix the bug where resizing the terminal while in input mode messes up the borders.
• (Hopefully) easier to follow control flow.