feat(config): add multiple file config sources

[gurinderu]

Description

Allow to pass --config argument multiple times and allow to pass multiple paths in FLUENCE_CONFIG env.

Motivation

Want to have a layered configuration: define based things in one file and override them with another config.

Related Issue(s)

https://linear.app/fluence/issue/NET-594/add-option-to-nox-cli-to-consume-several-configtomls
https://linear.app/fluence/issue/NET-616/remove-unused-options-in-nox-config

Proposed Changes

The initial file for loading is a Config.toml located near the nox binary file but it is not required.
The second priority is all files from FLUENCE_CONFIG env, separated by comma (,)
The last priority is files passed by the --config argument. The last config has the higher priority and overrides provided values from previous configs. All files provided by FLUENCE_CONFIG and --config should exist.

Additional Notes

Also removed unused values in configs.

Checklist

• The code follows the project's coding conventions and style guidelines.
• All tests related to the changes have passed successfully.
• Documentation has been updated to reflect the changes (if applicable).
• All new and existing unit tests have passed.
• I have self-reviewed my code and ensured its quality.
• I have added/updated necessary comments to aid understanding.

Reviewer Checklist

• Code has been reviewed for quality and adherence to guidelines.
• Tests have been reviewed and are sufficient to validate the changes.
• Documentation has been reviewed and is up to date.
• Any questions or concerns have been addressed.

[linear]

NET-594 Add option to Nox CLI to consume several Config.tomls

--config should become repeatable, and these configs should be merged according to Layered Config logic

[folex]

What about --config + --configs, where former always has the lowest priority?

I remember @nahsi said it's important cuz Ansible can reorder flags.

[gurinderu]

What about --config + --configs, where former always has the lowest priority?

I remember @nahsi said it's important cuz Ansible can reorder flags.

I have discussed these options with @nahsi and it is not the ansible problem. It is a problem with some cases (like jinja2) when software uses a map for args instead of vec. The map doesn't have the order. Also, he showed as an example a consul agent, but it works in the same way (you can pass -config-file multiple times and the last has higher priority and overrides the previous)