Add Feature Flag's Active Property to State

What does this MR do?

Begins the process of building the frontend of #13416 (closed) by making the active property available through Vuex.

As this will ultimately be behind the feature flag featureFlagToggle, I've elected to not include a changelog.

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers