Android color issues on 6.x

[LukasPaczos]

Refs. mapbox/mapbox-navigation-android#1045.

As seen in mapbox/mapbox-navigation-android#1045, on v6.2.0 Android colors are being parsed incorrectly resulting in a black fill.

Also, on all v6.x versions, excluding v6.2.0, the Android colors that have modified alpha component are also parsed incorrectly where alpha is ignored and the color is treated as fully opaque (unless the alpha value is 0).

All above issues refer to Expression#color expression. The workaround is to always use Expression#rgb or Expressions#rgba, for example instead of

layer.setProperties(
  fillColor(
    interpolate(
      exponential(0.8f),
      zoom(),
      stop(1, color(Color.GREEN)),
      stop(4, color(Color.BLUE)),
      stop(12, color(ContextCompat.getColor(this, R.color.red_with_alpha))),
      stop(20, color(Color.BLACK))
    )
  )
);

you should use

layer.setProperties(
  fillColor(
    interpolate(
      exponential(0.8f),
      zoom(),
      stop(1, rgb(0, 255, 0)),
      stop(4, rgb(0, 0, 255)),
      stop(12, rgba(255, 0, 0, 0.25)),
      stop(20, rgb(0, 0, 0))
    )
  )
);

/cc @tobrun @Guardiola31337 @danesfeder @langsmith