Dependencies on Python2

The [Diagnostic Extension](https://github.com/Azure/azure-linux-extensions/tree/master/Diagnostic) explicitly requires Python 2 to function.

The [OMS Extension](https://github.com/Azure/azure-linux-extensions/blob/master/OmsAgent/omsagent_shim.sh) will run on Python 2 or Python 3 but prefers Python 2.

Python 2 has been end-of-life for nearly two years, and is not receiving further security fixes. It is no longer included in Ubuntu distros by default, and while RHEL is supporting it in version 8 no updates are being backported to version 7 or earlier.

Is there an estimate to when extensions will be updated to both support and prioritize Python 3 in order to work on modern operating systems? We have organization-wide logging requirements that are achieved using these agents, but as of now we must manually install deprecated software and packages to use them. We're stuck in a scenario where we have a requirement to use the extensions but also a requirement to not use EOL software in production.

Start by inspecting the Diagnostic Extension linked in the issue and OmsAgent/omsagent_shim.sh, focusing on their Python version requirements and interpreter selection. Determine the extension entry points and package assumptions before defining the compatibility work; done means both extensions support and prioritize Python 3 on modern operating systems without requiring deprecated Python 2 software.

Written by the indexing model from the issue text.