[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
• 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
• Figure out slot visualization. Inspiration:
  • https://next.mui.com/x/react-date-pickers/date-picker/#customization
  • https://mantine.dev/core/autocomplete/#styles-api

Search keywords: docs slot pattern