Hotkey conflict prompt

This is based on top of https://github.com/CleverRaven/Cataclysm-DDA/pull/7291, which isn't merged yet. The relevant commit is https://github.com/lucianposton/Cataclysm-DDA/commit/a132a35f32e9fd7dd998b5d7078c76c7fb64c392

It is a pain to manually remove conflicting keybindings, so I wanted to way to handle conflicts. This patch adds a Y/N prompt to clear all conflicting keybindings when trying to add a keybinding.