Add AiCatalogItem.configurationForProject field

What does this MR do and why?

Add a new AiCatalogItem.configurationForProject GraphQL field.

The field returns the Ai::Catalog::ItemConsumer (referred to as a item configuration in GraphQL) for an AI Catalog item and the given project.

• #577040

How to set up and validate locally

Enable the global_ai_catalog flag.

(Optional). Patch your local to allow any project to create AI Catalog items.

diff --git a/ee/app/models/ee/project.rb b/ee/app/models/ee/project.rb
index dc8c5541fcea..c6ac444489ec 100644
--- a/ee/app/models/ee/project.rb
+++ b/ee/app/models/ee/project.rb
@@ -622,6 +622,7 @@ def suggested_reviewers_available?
       end

       def ai_catalog_available?
+        return true
         duo_features_enabled && ::Gitlab::Llm::StageCheck.available?(self, :ai_catalog)
       end
       strong_memoize_attr :ai_catalog_available?

Visit http://gdk.test:3000/explore/ai-catalog/agents/ and create some agents for a project https://docs.gitlab.com/user/duo_agent_platform/agents/#create-an-agent.

Add one of the agents to the project https://docs.gitlab.com/user/duo_agent_platform/agents/#enable-an-agent.

Now visit http://gdk.test:3000/-/graphql-explorer and perform some GraphQL queries, substitute <ITEM_ID> with the ID of the agent (visible when viewing the agent in the AI Catalog) and <PROJECT_ID> with your project ID:

Query using the agent ID you added to the project.

{
  aiCatalogItem(id: "gid://gitlab/Ai::Catalog::Item/<ITEM_ID>") {
    id
    configurationForProject(projectId: "gid://gitlab/Project/<PROJECT_ID>") {
      id
      enabled
    }
  }
}

You should get a response similar to:

{
  "data": {
    "aiCatalogItem": {
      "id": "gid://gitlab/Ai::Catalog::Item/192",
      "configurationForProject": {
        "id": "gid://gitlab/Ai::Catalog::ItemConsumer/39",
        "enabled": true
      }
    }
  },
  "correlationId": "01K852F1A8RGHD6TH7EVK98TJS"
}

Now query for the agent you did not add to the project, you should get a response similar to:

{
  "data": {
    "aiCatalogItem": {
      "id": "gid://gitlab/Ai::Catalog::Item/191",
      "configurationForProject": null
    }
  },
  "correlationId": "01K85437PZAXEMY46J19HABFMM"
}

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Related to #577040