Adding support for more PyPy versions and installing them on-flight

[maxim-lobanov]

Note

Recently, GitHub Actions task actions/setup-python was updated to allow installation of PyPy on-flight. We have changed syntax and now customers can specify exact PyPy and Python version via syntax like

pypy-3.6-v7.3.3
pypy-3.6-v7.3.x
pypy-3.6-v7.x
pypy-3.6 (pypy-3.7, pypy-2.7) (points to latest version of PyPy)
pypy-3.6-v7.3.3rc1
pypy-3.6-nightly

We propose integration these changes to UsePython task too.
You can find detailed information in actions/setup-python#168

Required Information

Question, Bug, or Feature?: Feature

Task Name: UsePython

[github-actions]

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