Improve & generalise keybind code

[MattSturgeon]

Building on #126's ModBindings refactor & toggle key handling, this PR:

• Generalizes the "combo key" logic in FreecamComboKeyMapping
• Moves control over keybind handlers to the keybinds themselves
• Introduces a builder to make defining different types of keybinds more declarative.
• Reduce the amount of "key handling" in Freecam to activateTripodHandler() & resetTripodHandler(),

I also removed ModBinding's "wrapper" methods;
They only existed to make using the enum values prettier, that is now unnecessary because the keybinds to define their own logic & don't care about the enum.
The one exception to this is in MinecraftMixin, however a couple .get()s is worth the reduced complexity/maintenance IMO.
If you disagree, then 00a5b73 can be dropped or reverted easily.

This PR does not affect the existing behavior in any way.

[hashalite]

Thanks, this is much better. Handling the keybinds directly in the tick was pretty sloppy. This makes it much easier to see what exactly each keybind does.