Replace KeyConflictContext enum with an Identifier-based solution #13

Existing enum would become something like kuma:universal, kuma:gui, kuma:world, and then there could be more specific ones like minecraft:debug for the set of debug keys, or something like vehicle-specific keys, etc.

Right now, for example, Vanilla's debug keys are showing as conflicts if you change them from the default, because Vanilla specially treats defaulted keys as non-conflicting (which is a bit of an issue of itself in a modded environment). Explicit more granular conflict scopes could solve this in a better way.