feat: use bind in flag dialog

Created by: FineFindus

Rewrites parts of the flag dialog to use bind to bind the settings to the switches directly. This removes the need for separate template callback functions for each switch. There is probably an even better way to emit a callback when the setting is changed but, besides directly listening to the setting, I'm not aware of it.

Also includes minor improvements like applying clippy, fmt and using urnwarp_or_else.