[core] Move hooks under component directories

[michaldudak]

Adopted the directory structure of the hooks in all new components: moved the hooks under the top-level component directory and created subdirectories per subcomponent.

I also created two index files under component directories: index.ts for subdirectory import and index.barrel.ts for directly re-exporting from the main library index file.

Also did a manual pass of sorting the relative imports by "distance" to the current module ("./" first, then "../", then "../../", etc.). Not super important but the code reads slightly better if the related imports are next to each other. We may consider enabling an eslint rule for it.

[mui-bot]

Netlify deploy preview

https://deploy-preview-405--base-ui.netlify.app/

Generated by :no_entry_sign: dangerJS against f7fb00afcbd708d67b63da2a1a37b77abac832fd

[oliviertassinari]

Could we add a note on why this change in the PR description? It looks like a breaking change for folks only using the hooks API.