[#1864] Add skip test decorators.


Problem description
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I am not happy with conditionals in tests and I am thinking that maybe we can implement those standard test skip conditions with decorators.

This branch explores ways in which we can implement decorators.


Changes description
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A dedicated decorated module was created to simplify imports.
Decorated needs to be imported, before using then.

I have added a decorator for os name and os family test filtering.


How to try and test the changes
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reviewers @alibotean 

Let me know if `decorator` module name make sense.

Let me know if decorator names are ok and what other decorator do you think that we need.