Migrate secret generator module to the new framework

Summary

The current secret generator module, which was ported from the previous GitLab Operator project, doesn't align with our new framework and makes the Secret generation workflow obscure. It currently enforces creating a Secret resource and annotating it. It comes with its own limitations.

We need to migrate this module and its core generators to fit into our new framework and its Inventory model, which is designed for generating objects.

Success criteria

• The secret generator module is fully integrated with the new framework and Inventory model, eliminating the need for creating and annotating separate Secret resources.
• Core generators within the module are refactored to work seamlessly, maintaining all existing functionality while improving workflow clarity and efficiency.