Operation (Query) Metrics

[chernser]

Summary

Adds class to represent metrics of an operation.

Checklist

Delete items not relevant to your PR:

• [x] Unit and integration tests covering the common scenarios were added
• [ ] A human-readable description of the changes was provided to include in CHANGELOG
• [ ] For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

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