[6.15.z] Enforce the Dynaconf validaton

[Satellite-QE]

Cherrypick of PR: #15289

Problem Statement

Currently, the configuration is not consistently validated. This can lead to:

• Uncaught errors in production: Invalid configurations can cause crashes, or unexpected behavior if not detected before deployment.
• Missed configuration changes: If validators are not updated alongside code changes, invalid configurations might slip through unnoticed.

Solution

Enforce the config validation.

Additionally, remove unused configuration files and their validators.

Benefits:

• prevent errors - catch configuration issues early to prevent crashes, and unexpected behavior,
• consistent configs - define valid formats and value ranges to reduce surprises.
• improve maintainability - validators act as documentation for configuration settings, making it easier for new developers to understand the project.
• early detection - identify configuration issues during development or deployment to save time and resources compared to fixing them in production.

Notes

I am open to changing the setting name and placement, robottelo.unit_test might not be the best choice.

[Satellite-QE]

trigger: test-robottelo

[Satellite-QE]

PRT Result

Build Number: 7415
Build Status: SUCCESS
PRT Comment: pytest /opt/app-root/src/robottelo/tests/foreman -v -m build_sanity --external-logging
Test Result : ======= 11 passed, 5448 deselected, 5553 warnings in 1659.43s (0:27:39) ========