Library-ify Common Functionality

Create libraries with nice straightforward interfaces to replace common functionality with multiple implementations across various modes. These libraries should have black-box implementations so that no messing about with internal structs is ever necessary (or possible). Ideal candidates would be anything that is tedious or error-prone to implement and is needed by multiple modes, or that would be likely to see use in multiple nodes if not for the effort of implementing it.

Potential candidates:

- [ ] Timing based functionality such as idle timers
- [ ] Handling "cheat code" style input
- [ ] Advanced input functionality, such as:
- [ ] Handling double-press or distinguishing between a quick press vs. a press-and-hold
- [ ] Button auto-repeating
- [ ] Button chording
- [ ] Using the touchpad as an arbitrary number of buttons
- [ ] Scaling touchpad output
- [ ] Touchpad swipes
- [ ] Managing high score lists
- [ ] Layout utilities such as centering text or drawing arrows
- [ ] Easier font handling (if we don't do memory-mapped assets)
- [ ] Advanced multi-level menus with native support for configuration values, confirmations, etc., independent of rendering
- [ ] Separate menu functionality from menu visuals/rendering