Collects Kibana Upgrade Assistant API output

It would be useful to see if the cluster is ready for upgrade when the version of the cluster is at latest minor (like 7.17.x)

Instead of asking for the Kibana upgrade_assistant API separately, can we run this as part of the Kibana diagnostics?

https://www.elastic.co/guide/en/kibana/8.11/upgrade-assistant-api-status.html
```
GET :/api/upgrade_assistant/status
```
example output:
```
{
"readyForUpgrade": false,
"cluster": [
{
"message": "Cluster deprecated issue",
"details":"You have 2 system indices that must be migrated and 5 Elasticsearch deprecation issues and 0 Kibana deprecation issues that must be resolved before upgrading."
}
]
}
```