CNDB-7237: add metrics to track replica response sizes

[djatnieks]

No description provided.

[github-actions]

Checklist before you submit for review

• This PR adheres to the Definition of Done
• Make sure there is a PR in the CNDB project updating the Converged Cassandra version
• Use NoSpamLogger for log lines that may appear frequently in the logs
• Verify test results on Butler
• Test coverage for new/modified code is > 80%
• Proper code formatting
• Proper title for each commit staring with the project-issue number, like CNDB-1234
• Each commit has a meaningful description
• Each commit is not very long and contains related changes
• Renames, moves and reformatting are in distinct commits
• All new files should contain the DataStax copyright header instead of the Apache License one

[djatnieks]

Just a few imports to clean up and changes to use Dispatcher.RequestTime.forImmediateExecution()

[sonarqubecloud]

Quality Gate failed

Failed conditions
78.3% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[cassci-bot]

❌ Build ds-cassandra-pr-gate/PR-1981 rejected by Butler

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1 regressions found
See build details here

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Found 1 new test failures

Test	Explanation	Runs	Upstream
o.a.c.service.reads.DigestResolverTest.multiThreadedNoRepairNeededReadCallback (compression)	REGRESSION	🔴	0 / 2

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Found 9 known test failures