KAFKA-19517: Include control records in LoadSummary#numRecords (#20206)

## Summary
jira: https://issues.apache.org/jira/browse/KAFKA-19517
Ensure `LoadSummary#numRecords` counts all records, including control
batches, to maintain consistency with numBytes.

## Test
`testLoading` now verifies `numRecords`.

Reviewers: Chia-Ping Tsai <[email protected]>, TengYao Chi
 <[email protected]>

Author: LoganZhuZzz

coordinator-common/src/main/java/org/apache/kafka/coordinator/common/runtime/CoordinatorLoaderImpl.java

@@ -214,6 +214,8 @@ private ReplayResult processMemoryRecords(
         for (MutableRecordBatch batch : memoryRecords.batches()) {
             if (batch.isControlBatch()) {
                 for (Record record : batch) {
+                    loadStats.numRecords++;
+
                     ControlRecordType controlRecord = ControlRecordType.parse(record.key());
                     if (controlRecord == ControlRecordType.COMMIT) {
                         if (LOG.isTraceEnabled()) {

coordinator-common/src/test/java/org/apache/kafka/coordinator/common/runtime/CoordinatorLoaderImplTest.java

@@ -183,7 +183,10 @@ void testLoading() throws Exception {
             when(log.read(8L, 1000, FetchIsolation.LOG_END, true))
                     .thenReturn(readResult5);
 
-            assertNotNull(loader.load(tp, coordinator).get(10, TimeUnit.SECONDS));
+            CoordinatorLoader.LoadSummary summary = loader.load(tp, coordinator).get(10, TimeUnit.SECONDS);
+            assertNotNull(summary);
+            // Includes 7 normal + 2 control (COMMIT, ABORT)
+            assertEquals(9, summary.numRecords());
 
             verify(coordinator).replay(0L, RecordBatch.NO_PRODUCER_ID, RecordBatch.NO_PRODUCER_EPOCH, new Tuple<>("k1", "v1"));
             verify(coordinator).replay(1L, RecordBatch.NO_PRODUCER_ID, RecordBatch.NO_PRODUCER_EPOCH, new Tuple<>("k2", "v2"));