Total Count for Terraform and Cluster GraphQL API

What does this MR do?

This will add a total count field to the following GraphQL queries:

• Terraform states
• Cluster agents
• Agent tokens

This will help us add pagination and additional views to our terraform and cluster list pages.

Screenshots (strongly suggested)

Query example:

query AgentsAndStates {
  project(fullPath: <project_path>) {    
    terraformStates {
      count
      nodes {
        id
      }
    }
    
    clusterAgents {
      count
      nodes {
        id
        tokens {
          count
          nodes {
            id
          }
        }
      }
    }
  }
}

query

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #267147 (closed)