Add Window.isWideColorGamut()

This API returns true when all the following conditions are met:
- The app has requested the window to be in wide color gamut mode
- The display has a wide color gamut
- The device supports wide color gamut rendering

Bug: 62832666
Test: CtsColorModeTest
Change-Id: Idae1527b88959689bb637b6dd4db756d09fabe77