CASSANDRA-21623 Report the number of rows replica filtering protection cached when it warns

[AhmedReda85]

Description

Previously, ReplicaFilteringProtection emitted a warning immediately upon crossing cachedRowsWarnThreshold + 1, reporting the threshold value rather than the actual maximum number of rows cached during the query.

This patch:

• Defers warning evaluation to QueryMergeListener.close() so the peak cached count (maxRowsCached) across the entire query is reported.
• Updates the warning message to:
  "Replica filtering protection has cached up to %d rows during query %s, which is over the warning threshold of %d rows defined by 'cached_replica_rows_warn_threshold' in cassandra.yaml."
• Suppresses the warning if the query already failed due to hitting cachedRowsFailThreshold (hitFailureThreshold = true).
• Updates failure message to clearly report currentRowsCached and cachedRowsFailThreshold.
• Adds entry to CHANGES.txt under 7.0.

Jira

• CASSANDRA-21623

Testing

• Updated ReplicaFilteringProtectionTest using AssertJ fluent assertions to verify the exact warning and failure messages.
• Ran targeted distributed test:
  ant test-jvm-dtest-some -Dtest.name=org.apache.cassandra.distributed.test.ReplicaFilteringProtectionTest (BUILD SUCCESSFUL).
• Passed git diff --check with zero whitespace errors.