[docs][material-ui] Improve documentation regarding slot pattern

[DiegoAndai]

After the slot pattern is standardized in Material UI (#41279, #41281), we should invest in documentation to share its mental model and mechanisms.

To do

• Copy Overriding component structure from Joy's docs: [docs] Add overriding-component-structure doc to Material UI #45186
• Fix: not all components have the slots section in their API, for example:
  • Slider doesn't: https://mui.com/material-ui/api/slider/#slider-prop-slots
  • Accordion does: https://mui.com/material-ui/api/accordion/#slots

Ideas

• Have an interactive slot visualization demo. Inspiration:
  • https://next.mui.com/x/react-date-pickers/date-picker/#customization
  • https://mantine.dev/core/autocomplete/#styles-api

Search keywords: docs slot pattern

[DiegoAndai]

@siriwatknp I created this issue a while ago with ideas on how to improve the slot pattern documentation

You already covered the first task in #45186.

I think we should also prioritize task two: "Fix: not all components have the slots section in their API"

Feel free to add more.

Task three is just an idea and probably not worth prioritizing. we can leave it for the future.