ColorScheme provides options for styling

- Add 5(!) lightweight classes for storing a design spec for a style.
- Add parameter to ColorScheme constructor for Style
- Add constructor replicating previous constructor for backwards
compatibility with existing code, uses Tonal Spot as tyle
- Reconfigure ColorScheme to use style to generate palettes

Test: atest ColorSchemeTest passes. Change default style to
style #1, make sure it works as intended, and matches what we've seen in
mocks. Continue through all 4 styles.
Bug: 213314628
Bug: 195969565

Change-Id: Iae2b4fc4ffd630bb4275f827798ae4643b230ae1