Add pmon daemons python3 build support

[Junchao-Mellanox]

- Why I did it

python2 is end of life and SONiC is going to support python3. This PR is going to support:

1. Build pmon daemons with python3
2. Install and run python3 version pmon daemons

- How I did it

1. Change pmon daemons make files to build bothe python2 and python3 whl
2. Change docker-platform-monitor make files to install both python2 and python3 whl
3. Change pmon docker startup files to start pmon daemons according to the supported platform API version

- How to verify it

1. Manual test to make sure all daemons are up and no error in syslog
2. Run platform regressions on a few platforms

- Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[Junchao-Mellanox]

The build issue will be fixed after merging sonic-net/sonic-platform-common#154 and moving submodule pointer.

[jleveque]

@Junchao-Mellanox: Please fix new conflicts.

[Junchao-Mellanox]

@Junchao-Mellanox: Please fix new conflicts.

Done

[jleveque]

Build failures in unit tests:

17:23:50  _____________________ ERROR collecting tests/test_xcvrd.py _____________________
17:23:50  tests/test_xcvrd.py:36: in <module>
17:23:50      class TestXcvrdScript(object):
17:23:50  tests/test_xcvrd.py:41: in TestXcvrdScript
17:23:50      @patch('xcvrd.xcvrd.logical_port_name_to_physical_port_list', MagicMock(return_value=[0]))
17:23:50  E   NameError: name 'patch' is not defined

Please check.

[Junchao-Mellanox]

17:23:50 _____________________ ERROR collecting tests/test_xcvrd.py _____________________
17:23:50 tests/test_xcvrd.py:36: in
17:23:50 class TestXcvrdScript(object):
17:23:50 tests/test_xcvrd.py:41: in TestXcvrdScript
17:23:50 @patch('xcvrd.xcvrd.logical_port_name_to_physical_port_list', MagicMock(return_value=[0]))
17:23:50 E NameError: name 'patch' is not defined

Hi @jleveque , this issue is introduced by commit:

commit b0be7ca52868064fb4e2b5ef9d44c774fdd87ade
Author: vdahiya12 <67608553+vdahiya12@users.noreply.github.com>
Date:   Tue Dec 15 04:10:34 2020 -0800

    [xcvrd] add unit test infrastructure and unit tests for xcvrd (#133)

    Summary:
    This PR provides the necessary infrastructure to add pytest support and integration in sonic-xcvrd submodule.
    This PR also adds unit tests for xcvrd daemon.
    What is the motivation for this PR?
    To add the pytest unittest support in sonic-platform-daemon, sonix-xcvrd daemon as well as add some unit tests
    Signed-off-by: vaibhav-dahiya <vdahiya@microsoft.com>

The error is introduced by line https://github.com/Azure/sonic-platform-daemons/blob/b674dffb717968b306b2bb967b0cbce74661a45f/sonic-xcvrd/tests/test_xcvrd.py#L9 . In this line it should import the package patch like:

if sys.version_info >= (3, 3):
    from unittest.mock import MagicMock, patch

I have created a PR to fix this. See sonic-net/sonic-platform-daemons#135

[jleveque]

@Junchao-Mellanox: Thank you for the fix! I merged it. Can you please update the submodule?

[Junchao-Mellanox]

Sure

[Junchao-Mellanox]

Hi @jleveque , please see #6247

[jleveque]

Hi @jleveque , please see #6247

Merged. Thanks again!

[jleveque]

Retest this please