Add hotkeys to the worktree-conflict menu shown when deleting a branch

[MitchellCash]

PR Description

The menu that appears when deleting a branch that's checked out in another worktree had no keybindings, forcing users to navigate with arrow keys. Add 's', 'd', and 'r' for switch / detach / remove.

Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalised (see here)
• If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
• Docs have been updated if necessary
• You've read through your own file changes for silly mistakes etc

[stefanhaller]

Looks like an easy change, but I'm undecided; the standard keybinding for deleting things in lazygit is d, so I feel that's what we should assign to "remove". Also, the "remove" item is probably going to change in the future to delete both the worktree and the branch, and we might reword this and the other items to make this clearer.

Holding off merging this for now for these reasons.

[MitchellCash]

That makes sense. Funnily, the reason I was messing around these parts was because I had the same thought to "delete both the worktree and the branch", as the UX for that flow wasn't great, especially as I have been using worktrees more and more.

Short of having that change code complete, I figured a hotkey for removal of the worktree would get me by 😄 Happy to wait, especially if the "delete both the worktree and the branch" is coming!