[docs] Overhaul autocomplete docs and demos

[mj12albert]

Preview: https://deploy-preview-48470--material-ui.netlify.app/material-ui/react-autocomplete/

This doc got messy over time, I revised the content and demos:

• Reorganized the headings around the main interaction modes: combobox, multiple-selection, freeSolo
• Added "Usage guidelines" which also replaces the "Accessibility" section, putting a11y guidance as the last section of the doc makes it look like a low priority thing. This is in the spirit of [docs] Add Accessibility section to all component demo pages #20600 but "Usage…" is better as it's more general and gives us room to include other important info here that may not necessarily be directly a11y related
• Consolidated a lot of sections under "Customization"

Demo changes:

• Replaced some demos with code snippets instead as it shows the concept better (hook setup, props and ref forwarding with a custom input element)
• Country selects: replaced the png flags with svg
• Single value rendering: changed the design, it's confusing to see "single value" in the title, but then see a demo that visually looks identical to a multi-select autocomplete
• Github picker: updated to look like the current GH design
• react-window demo: polished the implementation, added aria-posinset/aria-setsize (re: Autodesk)
• They all use shared data when possible (the movies or countries dataset), no need to duplicate the IMDB data across so many demos. Also updated the IMDB top 100 dataset itself)

[code-infra-dashboard]

Deploy preview

• docs/data/material/components/autocomplete/autocomplete.md
• docs/data/material/migration/migrating-from-deprecated-apis/migrating-from-deprecated-apis.md
• docs/data/material/migration/upgrade-to-v9/upgrade-to-v9.md

Bundle size

Bundle	Parsed size	Gzip size
@mui/material	0B(0.00%)	0B(0.00%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/private-theming	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

Details of bundle changes

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