Revert "Don't fail the build if @types/ packages appear to be missing"

[eps1lon]

This reverts commit 637033c.

What wasn't clear originally is that we require that required packages have their package.json resolvable. So either they don't have an exports field, or their package.json is listed in the exports field. The React beta types didn't have package.json entry in exports so we accidentally thought they weren't installed.

I published 19.0.0-beta.2 that has package.json in exports so we can restore the old behavior. It's still questionable IMO to do all that I/O work just for a nicer error message that may contain false-positive but that's for another time.

[ijjk]

Failing test suites

Commit: 6d7a648

TURBOPACK=1 pnpm test-start test/e2e/app-dir/app-static/app-static-custom-handler.test.ts (turbopack)

• app-dir static/dynamic handling > should have deterministic etag across revalidates

Expand output

● app-dir static/dynamic handling › should have deterministic etag across revalidates

Failing test passed even though it was supposed to fail. Remove `.failing` to remove error.

  621 |
  622 |   if (isNextStart) {
> 623 |     it.failing(
      |        ^
  624 |       'should have deterministic etag across revalidates',
  625 |       async () => {
  626 |         const initialRes = await next.fetch(

  at failing (e2e/app-dir/app-static/app-static.test.ts:623:8)
  at Object.describe (e2e/app-dir/app-static/app-static.test.ts:17:1)
  at Object.require (e2e/app-dir/app-static/app-static-custom-handler.test.ts:2:1)

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