DNS resolution across VPCs connected via S2S VPN

##### ISSUE TYPE

* Feature Idea

##### COMPONENT NAME

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VR
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##### CLOUDSTACK VERSION

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4.20
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##### CONFIGURATION

##### OS / ENVIRONMENT

##### SUMMARY

Current VR only resolve its own Guest Network DNS zone record and external records. When two or more peered VPC network, user has to manage the host resolution either by host file or create another forwarder point to VR in upstream DNS. I would say it would be more useful if we populate all DNS record across each peered zone VR with proper domain suffix. So the user do not need to discover new IP changes from peered zone.

##### STEPS TO REPRODUCE

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##### EXPECTED RESULTS

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##### ACTUAL RESULTS

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首先检查 CloudStack VR 组件，以及在 4.20 版本中如何表示已建立对等连接的 VPC DNS 区域。在确定相关实现和测试之前，明确预期的域名后缀、记录传播行为和面向用户的使用方式；完成的标准是，无需管理 hosts 文件或上游转发器，DNS 解析即可在已建立对等连接的 VPC 之间正常工作。

由索引模型根据 Issue 内容生成。