[core] Use exports instead of aliases where possible

[eps1lon]

Based on #25795

We have this kind of dangerous stack of technical debt that is pinning us down:

1. Can't use exports with webpack 4
   1. Can't use webpack 5 because of inline loader not migrateable to webpack 5 when used in require.context webpack/webpack#12900
      1. Can't resolve inline loader not migrateable to webpack 5 when used in require.context webpack/webpack#12900 with getStaticProps because of getStaticProps on _app vercel/next.js#10949
   2. Can't use webpack 5 because Bundle is invalid when used in an existing repository codymikol/karma-webpack#505
      1. Can't drop karma because there's no alternative (I have no idea how one would use browserstack)
2. Can't use exports because of Support for package.json exports and imports ? import-js/eslint-plugin-import#1868 (arguably the easiest since we should just be able to drop import/resolve)

[mui-pr-bot]

Bundle size will be reported once Azure build #26190 finishes.

Generated by 🚫 dangerJS against 7b5ca03

[eps1lon]

Would be nice but breaks down in packages where we mix index.ts and index.js. Since these are just files that define the public interface via import/export we should convert them to TypeScript anyway.

But there are some moving parts that need to be solved first. Considering we can't get rid of custom aliasing solutions anyway (see PR description) I'm closing until we can migrate completely.