Configure LayoutOptimizer default / convenience for testing or organize various configs better

[sandsq]

Lots of lines required to set up a layer optimizer or to change the default. Add some additional constructors, or maybe add some initialization function that takes all the (changed) configs and updates the relevant parts (like changing the keycode configs should change the dataset, etc.)

[sandsq]

moved some dataset configs from LayoutOptimizer to the config, added activate function that regenerates keycodes based on keycode config and call it at the beginning of optimize, generate dataset from dataset paths at the beginning of config rather than actually store the datasets in the optimizer struct