KAFKA-15330: Add missing documentation of metrics introduced as part of KAFKA-15028 (#14480)

I've added details for VerificationFailureRate and VerificationTimeMs.

I considered adding the documentation for the AddPartitionsToTxnVerification metrics, but I noticed that all the request metrics simply listed Produce|FetchConsumer|FetchFollower. If we don't already report the AddPartitionsToTxn request metrics in this file, it doesn't make sense to add the verification variant. (As well as all the other APIs we report)

Filed a followup jira if we want to redo that whole section.

Reviewers: Reviewers: Divij Vaidya <diviv@amazon.com>

docs/ops.html

@@ -1789,6 +1789,16 @@ $ bin/kafka-acls.sh \
         <td>kafka.server:type=transaction-coordinator-metrics,name=partition-load-time-avg</td>
         <td>average time, in milliseconds, it took to load transaction metadata from the consumer offset partitions loaded in the last 30 seconds (including time spent waiting for the loading task to be scheduled)</td>
       </tr>
+      <tr>
+        <td>Rate of transactional verification errors</td>
+        <td>kafka.server:type=AddPartitionsToTxnManager,name=VerificationFailureRate</td>
+        <td>Rate of verifications that returned in failure either from the AddPartitionsToTxn API response or through errors in the AddPartitionsToTxnManager. In steady state 0, but transient errors are expected during rolls and reassignments of the transactional state partition.</td>
+      </tr>
+      <tr>
+        <td>Time to verify a transactional request</td>
+        <td>kafka.server:type=AddPartitionsToTxnManager,name=VerificationTimeMs</td>
+        <td>The amount of time queueing while a possible previous request is in-flight plus the round trip to the transaction coordinator to verify (or not verify)</td>
+      </tr>
       <tr>
         <td>Consumer Group Offset Count</td>
         <td>kafka.server:type=GroupMetadataManager,name=NumOffsets</td>