CASSANDRA-21321: add per-table RowsRead and RowsMutated counters

[shiroonigami23-ui]

What is this

Adds per-table row throughput counters so operators can track rows read/mutated at table granularity.

JIRA

• CASSANDRA-21321

Changes

• Added RowsRead and RowsMutated counters to TableMetrics.
• Added RowsRead and RowsMutated keyspace-level counters derived from table metrics.
• Wired read metric recording to increment table RowsRead in SelectStatement path.
• Wired write metric recording to increment table RowsMutated from PartitionUpdate metadata in mutation paths.
• Extended ClientRequestRowAndColumnMetricsTest with assertions for table-level row counters.

Testing

• Unable to run unit tests in this environment because ant is not installed (ant: command not found on Windows shell).
• Verified call sites and diffs for signature and metric wiring.