Improve configuration and secrets management

[jychp]

In the current version, configuration can be painfull because it's inconsistant.

Exemple :

• GSuite intel use hardcoded VAR ENV
• GitHub use VAR ENV defined by an argparse argument

Creating new intel lead to many errors.

Consider switching to DynaConf (or other similar package) to :

• load non sensitive configuration from file
• override that conf with env
• use autoload (.env)
• add Vault support for secrets

I can help for the migration.

[juju4]

There are certainly options where a real configuration file would be better than just cli or environment variable (some source for which query could be customizable for example)
As for secrets, I would want to be able to fetch them from cloud vault (azure keyvault & co), not just hashicorp vault.

This could also help to make cartography poll only sources for which it has configuration, instead of always doing all and output unneeded error messages.

[achantavy]

Config file support in progress in #1124