Hotkey conflict prompt

Reviewers, please review and merge https://github.com/CleverRaven/Cataclysm-DDA/pull/7291 before this. This PR shares most its commits with that one, so once it is merged, this PR will be easier to review.

This is based on top of https://github.com/CleverRaven/Cataclysm-DDA/pull/7291, which isn't merged yet. The only new commit here (that isn't in https://github.com/CleverRaven/Cataclysm-DDA/pull/7291) is https://github.com/lucianposton/Cataclysm-DDA/commit/5e17fed4a911f6eaf0e8c0748baf517029d9b1f9

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.