Redesign ui tests with STEPS-architecture

Summary
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Redesign horizon ui autotests which will be based on STEPS-methodology to provide scalable, modular and portable code.

Current situation
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Selenium UI autotests for horizon have difficult code to understand. This increases the threshold of entering a new employee. They are difficult to debug. They are not scalable for new js-saturated angular interface. They are not support forms with dynamic-appearing fields. They are not support parallel launching.

Proposition
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There are UI autotests for horizon, which are based on STEPS-architecture: https://github.com/Mirantis/mos-horizon/tree/v9.1/. They are modular, scalable, stable and easy to debug. They are support new angular interface as easy as default html interface. And they already include tests for containers and instances with angular interface. They use pytest to launch so they support parallel launching too.
I'm inclined to believe, they must be ported to upstream.

Milestones
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1. Create non-voting job gate-horizon-dsvm-integration-new-design to launch these tests
2. Port core framework of these tests with users tests to show that they are stable, more readable and flexible that current UI tests.
3. Step-by-step port other tests.
4. Disable current UI tests and add voting privilege for new job.