Address Slider feedback

[joshwooding]

There's feedback from #3296 that needs to be addressed before it moves to core.

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1. A11y review
2. Remove a11y cursor interaction docs since not specific to slider
3. With input docs
4. With form field docs
5. Custom step docs and examples
6. Aria-label behaviour
7. onChange not returning an event (needs to be tested)
8. realHover usage in tests
9. missing tests for min and max, passing in a custom step vs not. etc.
10. max-width
11. padding on the label
12. default values not being inline
13. JSDoc review
14. defaultValue relation to min
15. clamp behaviour between controlled and uncontrolled
16. extra type definitions
17. type cast usage
18. focussed vs focused
19. Label being used instead of body text (semantics and styling)
20. Using window directly instead of targetWindow
21. toFixed(1) being used
22. non-nullable being used
23. setValue logic
24. Inconsistent format from percentage based utils
25. QA stories being separate
26. aria-labels used in stories/examples
27. Slider description on the site only mentions single slider
28. Check Keyboard behaviour docs covers all behaviour

[mark-tate]

Lungo Goal: no dev capacity

[mark-tate]

Can pull back into Q1 if there is a stakeholder who needs it, contact the team

[bhoppers2008]

To be addressed in Q2.

[bhoppers2008]

Picked up to review the existing code. @tayyabataimur to catch up with Josh.
Goal: Understand remaining requirements.

[tayyabataimur]

Took a look at the Slider component and its feedback and can split the work as following for easier reviews:

1. Code refactoring, improvements and optimization
2. Update site documentation, examples and QA stories
3. A11Y review with Jake and Josh and perform any follow-up tasks