Previously, we were guessing whether something is optional from the
comment (looking for stuff like "defaults to" or "optional").
To remove this error-prone technique, every optional property or
argument (but not option) is explicitly marked with "?".
As a result, fix documentation issues:
- Removed `TestStep.data` that is not a thing.
- Added `TestConfig.name` documentation.
- Refined a lot of optional types in the documentation.
- Aligned `test.fail()` and `test.slow()` docs with `test.skip()`.
- Strict set of docs vs types inconsistensies in the generator
Soft expects will still fail the test, but will not abort it's execution. As a consequence of this:
- `TestResult` now might have multiple errors, which is reflected with a new `testResult.erros: TestError[]` field.
- `TestInfo` now might have multiple errors as well, which is reflected with a new `testInfo.errors: TestError[]` field.
Fixes#7819
