Enable filtering with custom health checks based on node attributes:
```
opensearch.optimizedHealthcheck.filters: {
  attribute_key: "attribute_value",
}
```

Also, fixes issue that expects the response to array when it was a
dictionary.

Issue:
#2214
#2203

Signed-off-by: Kawika Avilla <[email protected]>
(cherry picked from commit e6bbb40)