em/remove-all command to ignore ambiguous emote names

Currently removing a bunch of emotes with the same name is a real slog. Usually you want to remove all or most of them. Let's add a `remove-all` command which ignores ambiguities and removes all emotes with the given name. Additionally, the disambiguation message "Multiple emotes were found with that name […]" should point out that the user can try em/remove-all instead.