Match Android's colors to design intent

May 2021 HCT code in Android ("CAM") gives results inconsistent with
HCT in design tooling. Using HCT solver ensures they match, allowing
design to verify their specs against the results in Android, derisking
the launch of theme variants.

HCT Solver is a standalone class that is easily integrated with Android
& Cam: when Cam.get(hue,chroma,tone) is called, it now calls
HctSolver.get(hue, chroma, tone).

HCT Solver was imported from google3, where it is tested against _all_
hex codes, both forward and reverse conversions. A number
of other tests cover all parts of the theming system, giving us high
confidence that there won't be a regression.

Test: atest ColorSchemeTest (unit test); atest SystemPaletteTest (CTS).
Spent ~4 hours trying a variety of wallpapers, and seed colors, and
used dumpsys to verify results match UX spec. Verify hex codes and HCT
values output by Android match those in design tooling via putting
hex codes into Monet Studio, and confirming the resulting HCT values
match the HCT values generated by Android.
Bug: 213314628
Change-Id: I95da1efacc2d61f19ce7f20efa3e7f70736258a9