Adding support for more PyPy versions and installing them on-flight (#168)

* add support to install pypy

* resolved comments, update readme, add e2e tests.

* resolve throw error

* Add pypy unit tests to cover code

* add tests

* Update test-pypy.yml

* Update test-python.yml

* Update test-python.yml

* Update README.md

* fixing tests

* change order

Co-authored-by: Maxim Lobanov <v-malob@microsoft.com>

* add pypy tests and fix issue with pypy-3-nightly

Co-authored-by: Maxim Lobanov <v-malob@microsoft.com>