Allure.NUnit: Report exceptions from OneTimeSetUp methods of class fixtures

#### I'm submitting a ...
- [ ] bug report
- [x] feature request
- [ ] support request => Please do not submit support request here, see note at the top of this template.

#### What is the current behavior?
If a [OneTimeSetUp] method fails, all test results of the class fixture aren't included in the report. The error, therefore, remains unreported.

#### What is the expected behavior?
If possible, skipped test results should be created. That might be tricky as, at first glance, NUnit doesn't provide the list of scheduled tests (it provides the list of all tests in the class instead; the user might have selected only a subset of them).

An alternative approach would be reporting the error in a surrogate test result. We already do something similar in Allure SpecFlow and Allure Reqnroll.

#### What is the motivation / use case for changing the behavior?
Include the information about the error that occurred during the run. That information might be important to the user.

Start by examining Allure.NUnit's handling of OneTimeSetUp failures and compare it with the analogous reporting in Allure SpecFlow and Allure Reqnroll. Done means the setup error is included in the Allure report, either through skipped test results or a surrogate test result.

Written by the indexing model from the issue text.