Draft: Separate ai_catalog_third_party_flows from ai_catalog_flows

What does this MR do and why?

This MR separate ai_catalog_third_party_flows from ai_catalog_flows. Before ai_catalog_flows had to be enabled for ai_catalog_third_party_flows to take effect. Now, it will be able to enable ai_catalog_third_party_flows without ai_catalog_flows.

This MR does not include the flow list on [PROJECT] > Automate > Flows yet, because the BE for showing third-party flows on project level isn't there yet. It only has effect on Explore > AI Catalog

This MR links into !208150 to make sure that there are no merge conflicts and the whole flow works once both MRs are merged into master.

References

Related to #575973

Screenshots or screen recordings

With both FF off

With only ai_catalog_flows on

With only ai_catalog_third_party_flows on

With both on

How to set up and validate locally

1. Prerequisite: You have a Duo workflow-enabled project.
2. Enable the feature flags global_ai_catalog, ai_catalog_flows, and ai_catalog_third_party_flows.
3. Go to Explore > AI Catalog > Flows. For example, https://gdk.test:3443/explore/ai-catalog/flows.
4. Click New flow and see both options available
5. Disable the feature flag ai_catalog_third_party_flows
6. See only the steps in create form
7. Disable the feature flag ai_catalog_flows but enable ai_catalog_third_party_flows again
8. See only the yml editor in create form
9. Disable both feature flags
10. Flows are not available

MR acceptance checklist

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