Stop wrapping/prepending error messages so that we do not loose the stack trace. For this, update a few manually thrown errors with better messages (usually including a file path).
Speed up locations by doing manual `sourceMapSupport.wrapCallSite()` for a single call site. Performance gain in the runner process with 100 files x 100 tests each:
- 25% on the fresh run without babel cache;
- 80% on the cached run where babel is almost instant.
Also some obvious cleanups around stack traces (removing unused code).
This fixes an issue where we incorrectly labeled and assigned ids for tests
that declared tests in require'd files or used test wrappers.
See new tests for examples.
- Source now lives at `src/test`.
- Former folio tests live at `tests/playwright-test`.
- We use `src/test/internal.ts` that exposes base test without
Playwright fixtures for most tests (to avoid modifications for now).
- Test types live in `types/testFoo.d.ts`.
- Stable test runner is installed to `tests/config/test-runner` during `npm install`.
- All deps including test-only are now listed in `package.json`.
Non-test deps must also be listed in `build_package.js` to get included.
