(Breaking Change) Move some hardcoded pixel values to reusable constants.

[Material] Text scale and wide label fixes for Slider and Range Slider value indicator shape (#35496)

Various bug fixes for Slider and Range Slider value indicator around accessibility and wide labels.

Fixes a bug in the Range Sider where the onChangeStart and onChangeEnd were not being called if the initial thumb selection came from a drag (rather than a tap).

[Material] Fix TextDirection and selected thumb for RangeSliderThumbShape and RangeSliderValueIndicatorShape (#34501)

Expose the RangeSlider's TextDirection in the RangeSliderThumbShape's abstract paint() method, and ensure that start and end thumb are non-null when being passed to the thumb and value indicator shape paint methods.

Creates a Material Design range slider.

The range slider is based off the updated slider, with the main difference being that it has 2 thumbs.
By default, the thumbs cannot pass each other and both the thumb and the value indicator create a stroke when they are overlapping for better visibility.