Add ability to version bump agents

What does this MR do and why?

This MR adds the ability to version bump agents.

The feature is behind a flag that is disabled by default.

• #560254 (closed)

How to set up and validate locally

Enable these two flags:

Feature.enable(:global_ai_catalog)
Feature.enable(:ai_catalog_enforce_readonly_versions)

Visit GraphQL Explorer: http://gdk.test:3000/-/graphql-explorer

Create a new agent:

mutation {
  aiCatalogAgentCreate(input: {
    projectId: "gid://gitlab/Project/1000000"
    name: "My name"
    description: "My description"
    release: true
    public: false
    systemPrompt: "My system prompt"
    userPrompt: "My user prompt"
  }) {
    errors
    item {
      id
      latestVersion {
        versionName
      }
    }
  }
}

Using the id of the agent you just created, use the aiCatalogAgentUpdate mutation to do a series of updates to the systemPrompt, changing its value for each update to create more versions.

You will see each released version is a "patch" release. You can also change versionBump to MINOR or MAJOR.

mutation {
  aiCatalogAgentUpdate(input: {
    id: "gid://gitlab/Ai::Catalog::Item/140"
    name: "My name"
    release: true
    versionBump: PATCH
    public: true
    systemPrompt: "New system prompt"
  }) {
    errors
    item {
      id
      name
      versions {
        count
        nodes {
          releasedAt
          released
          versionName
          ...on AiCatalogAgentVersion {
            systemPrompt
          }
        }
      }
    }
  }
}

Now make a series of update mutation calls, but only change the versionBump argument to PATCH, MINOR or MAJOR. Notice that now you can't version bump its versionName as the version has been released.

Now make another update mutation call, this time change systemPrompt and have release: false so that you create a new draft version.

Now make a series of update mutation calls, but only change the versionBump argument to PATCH, MINORorMAJOR. Notice that you can version bump its versionName` as the version is a draft version.

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Related to #560254 (closed)