Add random chars as the job name suffix by default on IT, avoid name collision

[bvolpato]

Parameterized / parallel tests have been suffering with flakes because of job name collision when only suffixed with timestamp:

com.google.api.client.googleapis.json.GoogleJsonResponseException: 409 Conflict
POST https://dataflow.googleapis.com/v1b3/projects/{PROJECT}/locations/us-central1/flexTemplates:launch
{
  "code": 409,
  "errors": [
    {
      "domain": "global",
      "message": "(78f666ea16e50f79): There is already an active job named test-jdbc-to-pubsub-20231115093811749. If you want to  submit a second job, try again by setting a different name.",
      "reason": "alreadyExists"
    }
  ],
  "message": "(78f666ea16e50f79): There is already an active job named test-jdbc-to-pubsub-20231115093811749. If you want to  submit a second job, try again by setting a different name.",
  "status": "ALREADY_EXISTS"
}

This will add more entropy and avoid that collision.

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[damondouglas]

LGTM Thank you, @bvolpato