CNDB-16277: Fix TombstoneOverwhelmingException being swallowed when tracking warnings (#2171)

### What is the issue

ReadCommandVerbHandler was catching RejectException and returning an
empty response instead of propagating the failure when warnings tracking
was enabled.

### What does this PR fix and why was it fixed

TombstoneOverwhelmingException is always re-thrown regardless of warning
tracking state.

Author: driftx

src/java/org/apache/cassandra/db/ReadCommandVerbHandler.java

@@ -23,6 +23,7 @@
 import org.slf4j.LoggerFactory;
 
 import org.apache.cassandra.config.DatabaseDescriptor;
+import org.apache.cassandra.db.filter.TombstoneOverwhelmingException;
 import org.apache.cassandra.db.partitions.UnfilteredPartitionIterator;
 import org.apache.cassandra.dht.Token;
 import org.apache.cassandra.exceptions.InvalidRequestException;
@@ -123,7 +124,10 @@ public void doVerb(Message<ReadCommand> message)
         }
         catch (RejectException e)
         {
-            if (!command.isTrackingWarnings())
+            // TombstoneOverwhelmingException should always be propagated as a failure,
+            // even when tracking warnings, as it indicates a guardrail violation that
+            // must be reported to the client
+            if (!command.isTrackingWarnings() || e instanceof TombstoneOverwhelmingException)
                 throw e;
 
             // make sure to log as the exception is swallowed