We used to not report fatal error and hang forever because worker
did not run any tests but also did not report any errors.
Also properly show stack-less errors.
This makes our suite structure the following:
```
Root(title='') > Project(title=projectName) > File(title=relativeFilePath) > ...suites > test
```
Removed `fullTitle()` because it is not used directly by anyone.
Default reporters now report each test as
```
[project-name] › relative/file/path.spec.ts:42:42 › suite subsuite test title
```
- 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.
