Display keybindings in help menu in sorted way

[fritzrehde]

There are different possibilities of how to sort the keybindings when displaying, but this is my preferred one: Sort according to their configuration hierarchy and insertion order: Larger (in terms of config hierarchy, e.g. cli > global toml file) keybindings should be closer to the top, and inside a common config hierarchy the order should be exactly the way it was specified by the user (in the toml file or via cli). This would be the most user-friendly implementation, it allows the user to see the keybindings just the way they ordered them. We could use indexmap to get a hashmap that retains insertion order.