[core] Rename directories to match the new package names

[mnajdova]

First of all, apologies for the big PR 🙏

The PR renames the old directories structure with a new one that reflects the new package names. Closes #28182

Recommend per commit review.

The first commit is the result of the following commands:

git mv packages/material-ui packages/mui-material
git mv packages/material-ui-codemod packages/mui-codemod
git mv packages/material-ui-lab packages/mui-lab
git mv packages/material-ui-unstyled packages/mui-core
git mv packages/material-ui-system packages/mui-system
git mv packages/material-ui-styles packages/mui-styles
git mv packages/material-ui-private-theming packages/mui-private-theming
git mv packages/material-ui-styled-engine packages/mui-styled-engine
git mv packages/material-ui-styled-engine-sc packages/mui-styled-engine-sc
git mv packages/material-ui-utils packages/mui-utils
git mv packages/material-ui-types packages/mui-types
git mv packages/material-ui-docs packages/mui-docs
git mv packages/material-ui-envinfo packages/mui-envinfo
git mv packages/material-ui-icons packages/mui-icons-material

The following commits are described by the commit messages.

[mui-pr-bot]

Details of bundle changes (experimental)

Generated by 🚫 dangerJS against ac76cab

[oliviertassinari]

The documentation is off https://deploy-preview-28185--material-ui.netlify.app/api/timeline-content/#import

[eps1lon]

Pushed some more changes and resolved #28185 (comment)

[mnajdova]

Pushed some more changes and resolved #28185 (comment)

Ah I wondered what happened 😄 Going to merge next now