feat(meta): add a rpc to fetch meta store endpoint

[chenzl25]

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What's changed and what's your intention?

• Related Tracking: Iceberg engine table #19418
• Add a rpc to fetch meta store endpoint info from meta for frontend.

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[yezizp2012]

Can you briefly introduce the motivation and further usage? Currently, there is indeed no interface exposed for the meta store endpoint.

[chenzl25]

Can you briefly introduce the motivation and further usage? Currently, there is indeed no interface exposed for the meta store endpoint.

In iceberg engine table, we want to use sql backend as the iceberg catalog, so other components like frontend need to know the endpoint of sql meta store to tell iceberg how to access it. #19577 (comment)