[SliderUnstyled] Improve value label display logic

[ZeeshanTamboli]

• I have followed (at least) the PR section of the contributing guide.

TO BE MERGED AFTER mui#35770.

Breaking Changes for MUI Base:

• The valueLabelDisplay prop is removed from SliderUnstyled. It was not working as intended in SliderUnstyled (See [docs] Customize valueLabel in SliderUnstyled with tailwind mui/material-ui#35398). You can instead provide a valueLabel slot with the slots prop API to show the value label:

- <SliderUnstyled valueLabelDisplay="on" />
+ <SliderUnstyled slots={{ valueLabel: SliderValueLabel }} /> 

The following demo shows how to show value label when it is hovered upon the thumb: https://deploy-preview-35479--material-ui.netlify.app/base/react-slider/#value-label

• The following classes are removed from sliderUnstyledClasses since they are not needed for value label:

- valueLabel
- valueLabelOpen
- valueLabelCircle
- valueLabelLabel

You can define your own classNames in the custom value label component and target them in CSS.

• The SliderValueLabelUnstyled component is removed from SliderUnstyled. You can provide your own custom component for the value label.

• The Value label component hierarchy structure is changed to avoid using React.cloneElement in value label. The value label is now inside the Thumb slot - Thumb -> Input, ValueLabel.

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Remove the SliderLabelValueUnstyled component from MUI Base and show the value label by simply hovering on the thumb in SliderUnstyled. Add demo to showcase it (preview below)

Closes mui#35398