Add a feature flag fiddling api for testing

Flux acceptance tests will need an api for getting the status of feature flags, as well twiddling the feature flag bits within the test. This could be an api as simple as `getFeatureFlag` and `setFeatureFlag`.

DOD:
- Feature flags can be checked and changed in flux acceptance tests

Start by locating the Flux acceptance tests and the existing feature-flag implementation or API entry points. Define how the test-facing getFeatureFlag and setFeatureFlag operations fit the current interfaces, then verify that Flux acceptance tests can check and change feature flags as described in the definition of done.

Written by the indexing model from the issue text.