feat: make privatelink.endpoint accept json array

[tabVersion]

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What's changed and what's your intention?

resolve cloud issue

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Release note

        // new syntax: endpoint can either be a string or a json array of strings
        // if it is a string, rewrite all broker addresses to the same endpoint
        // eg. privatelink.endpoint='some_url'
        // ==> broker1:9092 -> some_url:9092, broker2:9093 -> some_url:9093
        //
        // if it is a json array, rewrite each broker address to the corresponding endpoint
        // eg. privatelink.endpoint = '[{"host": "aaaa"}, {"host": "bbbb"}, {"host": "cccc"}]'
        // ==> broker1:9092 -> aaaa:9092, broker2:9093 -> bbbb:9093, broker3:9094 -> cccc:9094

[tabVersion]

here we introduce a potential risk is if the user input an illegal json, which cannot be parsed, we will see it as a string, instead of returning error. The case seems acceptable to me because he cannot connect to the broker using the wrong endpoint addr and he will find out later.

[tabVersion]

convert to draft for now as the poc user does not need it.