Linux diagnostics failed to be processed/installed due to a wrong python binary tried to be used

When I check the logs of the failure :

I don't think making an assumption is a good idea when installing software, be it extensions or not.
```
[ExtensionOperationError] Non-zero exit code: 127, /var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.141/diagnostic.py -install [stdout] [stderr] /usr/bin/env: ‘python’: No such file or directory
```
This is for a Debian 12 Bookworm machine.

Start by locating the extension's diagnostic.py entry point and reproduce the installation failure on a Debian 12 system. Done means the installation no longer tries the unavailable `python` binary and the Linux diagnostics are processed and installed successfully.

Written by the indexing model from the issue text.