[ISSUE #3369][FEAT]create topic with broker addr or name or none

[Tomilla]

What is the purpose of the change

Create Topic with optional argument:

• broker address(current implement is required argument): direct invoke createTopic API with address
• broker name: in first, client will call getBrokerClusterInfo, then resolve name to address, then invoke API
• nothing: like broker name case, but it will apply createTopic on all addresses that getBrokerClusterInfo returned.

Brief changelog

1. implement GetBrokerClusterInfo of Admin interface. in the meanwhile, there are integer type keys in RocketMQ Java Server response of GetBrokerClusterInfo, Golang JSON library cannot unmarshal them directly. So I fixed the JSON didn't conform to the JSON specification (JSON keys should always be strings, don't use int as a key).

rocketmq-client-go/admin/admin.go

Line 39 in 7eedaf9

//GetBrokerClusterInfo(ctx context.Context) (*remote.RemotingCommand, error)

2. introduce another CreateTopic implementation like sarama, without brokerAddr as input.

rocketmq-client-go/admin/admin.go

Line 158 in 7eedaf9

// TODO: another implementation like sarama, without brokerAddr as input

3. add optional flag for createTopic to avoid override same name topic configuration. for back compatibility, it is false by default.

Verifying this change

I've update the examples/admin/topic/main.go file, which demonstrates all new features such as:

• get broker cluster info;
• create topic without broker address;
• create topic with "NotOverride" check.

furthermore, I also wrote UnitTest and BenchmarkTest for JSON integer key rectify function.

Related to apache/rocketmq#3369

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[Tomilla]

Compare this to @Slideee PR (#1006), which tried to import a go-version JavaScript interpreter into the project, but that was only used in very small cases (json loading), so it is overkill for our limited needs.

My solution is green and doesn't introduce any 3rd party heavyweight modules. furthermore, since it all uses native syntax or built-in libraries, it is better performance than adding a VM layer.

Related to #1005

[HubQin]

it's a nice feature!

[Tomilla]

@HubQin
it's a nice feature!

The code for this PR has been running stably within our company for more than half a year, indicating that there is no problem with the logic of the code itself.

However, It is unclear what the maintainer @xujianhai666 thinks about this feature merge request? If there is a need for more test cases, or additional documentation or something, please let me know exactly what to do.