Agentic Chat general availability policy

What does this MR do and why?

The MR introduces a new policy for Duo agentic Chat. The policy relies on:

• availability of classical Duo Chat as the base
• extends it to check the duo_agentic_chat feature flag (introduced in this MR as well)
• extends it to check for the "Experimental AI features" setting

Here's the visual representation of the policy:

In addition to the policy, the MR also extends the Project GraphQL query endpoint to return the duoAgenticChatAvailable field, that indicates whether the Duo agentic Chat is available for that or another project. This capability is needed for the checks in VSCode extension (whether to show Duo agentic Chat or not).

This results in the policy to be true only when:

• The current license is Premium or Ultimate
• Project has Duo enabled
• Group or higher level has the "Feature preview" (experimental) enabled

References

How to set up and validate locally

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #540750