Bug: listHostsMetrics response mapping mismatch (clustermetrics -> cluster) causes null parsing

The CloudStack backend response for listClustersMetrics "command" has changed its JSON structure, but the cloudstack-go wrapper is still parsing the old field (hostmetrics).

This results in host metrics being returned as null in the Go SDK response.

API: listClustersMetrics (command)
Client: github.com/apache/cloudstack-go/v2

Key change:
The backend now returns metrics under the field host, not hostmetrics.

从 cloudstack-go wrapper 中的 listClustersMetrics API 映射开始，并将其 response 字段处理方式与此处描述的 backend response 进行比较。确认主机指标是从 host 而不是 hostmetrics 读取的，然后运行相关的 SDK 测试或发起一个 listClustersMetrics 请求，以确认返回的指标不再是 null。已有一个开放的 pull request 处理此问题。

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