Improve `type: :ops` definition and purpose

What does this MR do?

This adds a RuboCop rule to ensure that ops feature flags are allowlisted.

This improves definition to indiciate that the first choice should always be development feature flags.

This is meant to resolve the #271384 to ensure that type: :ops is reduced to minimum.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content