Add GraphQL mutation to revoke an agent token

What does this MR do and why?

Adds a GraphQL mutation to revoke a Cluster Agent token via the recently added status field.

Screenshots or screen recordings

GraphQL request:

mutation {
  clusterAgentTokenRevoke(input: { id: "gid://gitlab/Clusters::AgentToken/119" } ) {
    errors
  }
}

Response:

{
  "data": {
    "clusterAgentTokenRevoke": {
      "errors": []
    }
  }
}

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

#348386 (closed)