Split Python files from ConfigMap

[LeoColomb]

The purpose of this PR is to isolate Python files used in the Helm chart to apply usual tests and checks on them.
This should help to maintain these scripts:

• Automatic lint/format/assertions based on Netbox org config (Introduce a linter workflow #326).
• Better dev environment with Python-related IDE extensions and integrations.
• Possibility to add integration tests, which could help to assess contributions like Adds support for multiple LDAP groups #318.
• Same features from Helm chart point of view.

From a more opinionated PoV, I believe keeping Python files away from Helm chart templating would ensure more stable scripts and less breaking changes there.