[xds]: export discoveryReq/Resp resource count, payload size metrics to help understand network bandwidth cost of control plane.

[stevenzzzz]

Title: export discoveryReq/Resp resource count, payload size metrics to help understand network bandwidth cost of control plane.

Description: export discoveryReq/Resp resource count, payload size metrics to help understand network bandwidth cost of control plane.

Metrics could be: Per request/response resource{added, removed} count, Raw protobuf config size

this way we can better understand the config plane network cost as well as data serialization/deserialization cost.

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Any extra documentation required to understand the issue.

[stevenzzzz]

@AndresGuedez @adisuissa @htuch

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or "no stalebot" or other activity occurs. Thank you for your contributions.

[github-actions[bot]]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted" or "no stalebot". Thank you for your contributions.

[stevenzzzz]

eh, @wbpcode @adisuissa I think we want to give this a shot?

[yannickepstein]

I would like to look into this, if no one else is working on it.