pytest support

[chidanandpujar]

pytest support for Unit tests

Refer #716

tests/unit# python3 -m pytest
==================================================================== test session starts ====================================================================
platform linux -- Python 3.12.0, pytest-8.3.4, pluggy-1.5.0
rootdir: /root/ansible_integration_test/ansible-junos-stdlib
collected 15 items                                                                                                                                          

test_command.py .....                                                                                                                                 [ 33%]
test_facts.py ..                                                                                                                                      [ 46%]
test_file_copy.py ..                                                                                                                                  [ 60%]
test_ping.py ...                                                                                                                                      [ 80%]
test_system.py ...