Hide self from step parameters by default #222 - deliver mentioned parameter

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#### 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?
self and cls parameters are deleted from step(allure.step) in report

#### If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem

#### What is the expected behavior?
I would like have self or cls in "step" print (allure.step). I would like to have special parameter mentioned in fixed issue https://github.com/allure-framework/allure-python/issues/222 or any other method to achieve this

#### What is the motivation / use case for changing the behavior?
"self" is important in my framework because it have __repr__ and i would like to see it in step parameters in report

#### Please tell us about your environment:

- Allure version: 2.14.0
- Test framework: pytest@6.2.4
- Allure adaptor: allure-pytest@2.9.43

#### Other information

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