Support admin GetBrokerClusterInfo method

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**BUG REPORT**
1. Please describe the issue you observed:

- What did you do (The steps to reproduce)?

- What did you expect to see?

- What did you see instead?

2. Please tell us about your environment:

- What is your OS?

- What is your client version?

- What is your RocketMQ version?

3. Other information (e.g. detailed explanation, logs, related issues, suggestions on how to fix, etc):

**FEATURE REQUEST**

1. Please describe the feature you are requesting.

2. Provide any additional detail on your proposed use case for this feature.

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4. If there are some sub-tasks using -[] for each subtask and create a corresponding issue to map to the sub task:

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Start by reviewing open pull request #1006, which is linked to this issue, and trace the Go client entry points it changes for the admin GetBrokerClusterInfo method. Done means the requested admin method is supported and the related checks in the pull request pass.

Written by the indexing model from the issue text.