Enable filtering agent tokens by status

What does this MR do and why?

Adds a status argument to the Agent tokens resolver, to allow retrieving only active (or revoked, if necessary) tokens.

Screenshots or screen recordings

GraphQL request:

{
  project(fullPath: "path/to/agent-config") {    
    clusterAgent(name:"my-agent") {
      name
      tokens(status: REVOKED) {
        nodes {
          name
          status
        }
      }
    }
  }
}

Response:

{
  "data": {
    "project": {
      "clusterAgent": {
        "name": "my-agent",
        "tokens": {
          "nodes": [
            {
              "name": "my-token",
              "status": "REVOKED"
            }
          ]
        }
      }
    }
  }
}

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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