CNDB-12781: POC: Read from storage in parallel when reading from multiple iterators (DO NOT MERGE)

[eolivelli]

What is the issue

This is a POC to see the impact of issuing parallel reads from storage while consuming many iterators at once.

The intent is to improve latency when the storage service is enabled, because in that case reads are sent in parallel to multiple nodes

What does this PR fix and why was it fixed

...

see https://github.com/riptano/cndb/issues/12781

[github-actions]

Checklist before you submit for review

• 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