Fix reference issue from the Theme and XML color in Gradient Drawable by

1. Change mGradientColors to a ColorStateList array
2. Update mGradientColors array by reading the Theme and XML color in UpdateGradientDrawableGradient function
3. Query state color in each instance of mGradientColors array in
ensureValidRect function for LinearGradient object creation.

Bug: 157969624
Test: android.graphics.drawable.cts.GradientDrawableTest suite
Change-Id: Ibbf2c5cb2846d75c53bd34a3f04661ae604e6745