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 (merged) 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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