Fix integration for Allure and pytest_bdd when test parameter is dict

[elchupanebrej]

Context

When do allure serve on the next generated report
https://gist.github.com/elchupanebrej/4b1d78096ac181ef56edd9b1a1549f57

Allure fails:
https://gist.github.com/elchupanebrej/e753d7d1005c811ff616417ae625df51

This happens because of dangerous serialization at

data = asdict(item, filter=lambda attr, value: not (type(value) != bool and not bool(value)))

Checklist

• Sign Allure CLA
• Provide unit tests

[CLAassistant]

All committers have signed the CLA.

[elchupanebrej]

@sseliverstov please review

[delatrie]

Scenario outline params now are always strings.
As for pytest params and step args, #845 adds a proper conversion to strings for them.