Made `ColorSelector` fully functional: added `onPress` handling, save buttons for the thread color, and modified the `ColorPickerModal` height to fit the smaller size of `ColorSelector` (as opposed to `ColorPicker`).
Full context in [[ https://linear.app/comm/issue/ENG-1001/redesign-native-colorpicker-component | Linear issue ]]. Phasing out `ColorPicker` can be handled in a future diff.