Add mypy checks

[RLKRo]

As mentioned here viewing codestyle check results is not convenient.

This pull request solves that problem in two ways:

1. codestyle1.yml -- produces the following output.
2. codestyle2.yml -- produces the following output.

In my opinion, the second solution is better.

[pseusys]

Second option is more obvious for sure. However:

1. Checkout and triple dependencies installation are required
2. What's the difference at all if in the end all checks should pass?..

I would suggest either leave the first one or use second with some dependency caching.

[kudep]

Second option is faster then our current unit-tests (because of that we do not have to wait three linting tests) and it's more atomic style. So I prefer the second one.

[kudep]

We will wait until the end of addon's mega-merges.

[kudep]

Do we need this PR, i think it can be closed

[RLKRo]

I think it should be used to add mypy check. The name of the branch is codestyle/add-mypy-check. So should probably just rename this PR.