chore: integrate knip and remove unused code, exports and dependencies

[ulrichstark]

Motivation

I attempted to integrate Knip into this project to automatically find and remove unused code, exports and dependencies. This PR is the result of this experiment. The knip config file is probably not optimal and I'm not sure if some removed exports might break the public API surface of vite, but nonetheless most findings are probably valuable.

Reproduce

To reproduce my changes, create the knip config of this PR and run following commands:

npx knip --fix --allow-remove-files
pnpm install
pnpm lint

Findings

• Uninstalled unused dependencies @types/express and vue-tsc from docs/package.json
• Deleted unused Vue component file SponsorBanner.vue from docs/.vitepress/theme/components
• Removed a lot of unused exports
• After removing the export keyword some members were completely unused like the esbuildPlugin function

Testing

Running pnpm test is still succeeds for me locally.

Proposed follow up changes

Maybe add knip as devDependency and run it in CI.

[ulrichstark]

I don't know why but I suddenly got these seemingly unrelated linting issues and fixed them in my previous commit:

/Users/uli/Desktop/vite/packages/vite/src/node/plugins/css.ts
  2008:41  error  Capturing group number 1 is defined but never used  regexp/no-unused-capturing-group
  2008:45  error  Capturing group number 2 is defined but never used  regexp/no-unused-capturing-group
  2010:24  error  Capturing group number 1 is defined but never used  regexp/no-unused-capturing-group

[ulrichstark]

Tests in CI failed after I applied the lint suggestions. Just reverted that commit.

[ulrichstark]

I'm closing this PR by splitting it up into #23381 and #23382.