Removes API dependency on composite identity onboarding and instance level Duo settings

What does this MR do and why?

We removed the composite identity settings in !222363 (merged)

This MR removes the composite identity onboarding dependency on duo_workflow API and concerns. It also removes the ::Ai::DuoWorkflow.enabled? check from presenter layer since it checks only for instance level settings, which should rather be checked for the container. This is being changed to project.duo_features_enabled or group.duo_features_enabled

References

Screenshots or screen recordings

	Before	After
Sessions menu

How to set up and validate locally

1. Go to instance level settings and turn off duo by default for the instance, docs
2. You should be able to use DAP flows, POST /workflows API should return a 201
3. Verify that you are able to see Generate MR with Duo , Convert to GitLab CI/CD and Fix Pipeline with Duo buttons

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