Tracking: Optimizations

## Optimizations

This issue tracks improvements that target resource usage: cpu, memory, binary size, etc.

### Performance
- [x] Optimise style diffing (ptr comparisons)
- [x] DOM "event presence" optimisation (bitmap?)
- [ ] Paint culling for non-root-viewport
- [ ] Limit damage to formatting context where appropriate
- [ ] Make use of REPAINT damage (don't repaint if no damage)

### Memory usage
- [ ] Stop using `taffy::Style`
- [ ] Fix known memory leaks
- [ ] Anonymous nodes
- [x] Parley font names

### Binary size
- [ ] Port resvg to fontations