**- 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