Add eval details for rego constraints.

[blkt]

Summary

This PR makes rego/constraints evaluation engine uniform with the rest of the rules using templates for evaluation details failures.

Fixes stacklok/minder-stories#43

Change Type

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

Unit tested.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[eleftherias]

@blkt could you link the commit to the user story https://github.com/stacklok/minder-stories/issues/43?

[blkt]

@eleftherias I was not aware of the story, this commit does not resolve it.
Edit: I forgot an important "not" in the previous statement.