Fix: close() never gets called for BatchSource (apache#7866)

Motivation
close() method never gets called in BatchSource

pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/source/batch/BatchSourceExecutor.java

@@ -183,6 +183,9 @@ private void stop() throws Exception {
       intermediateTopicConsumer.close();
       intermediateTopicConsumer = null;
     }
+    if (batchSource != null) {
+      batchSource.close();
+    }
   }
 
   private void setupInstanceSubscription() {

pulsar-functions/instance/src/test/java/org/apache/pulsar/functions/source/batch/BatchSourceExecutorTest.java

@@ -54,6 +54,8 @@ public static class TestBatchSource implements BatchSource<String> {
     private static int discoverCount;
     @Getter
     private static int recordCount;
+    @Getter
+    private static int closeCount;
     private Record record = Mockito.mock(Record.class);
     public TestBatchSource() { }
 
@@ -87,7 +89,7 @@ public Record<String> readNext() throws Exception {
 
     @Override
     public void close() throws Exception {
-
+      closeCount++;
     }
   }
 
@@ -98,6 +100,8 @@ public static class TestBatchPushSource extends BatchPushSource<String> {
     private static int discoverCount;
     @Getter
     private static int recordCount;
+    @Getter
+    private static int closeCount;
     private Record record = Mockito.mock(Record.class);
     public TestBatchPushSource() { }
 
@@ -127,7 +131,7 @@ public void prepare(byte[] task) throws Exception {
 
     @Override
     public void close() throws Exception {
-
+      closeCount++;
     }
   }
 
@@ -344,6 +348,8 @@ public void testLifeCycle() throws Exception {
     discoveryBarrier.await();
     Assert.assertTrue(testBatchSource.getDiscoverCount() >= 2);
     Assert.assertTrue(testBatchSource.getDiscoverCount() <= 3);
+    batchSourceExecutor.close();
+    Assert.assertEquals(testBatchSource.getCloseCount(), 1);
   }
 
   @Test
@@ -362,5 +368,7 @@ public void testPushLifeCycle() throws Exception {
     discoveryBarrier.await();
     Assert.assertTrue(testBatchPushSource.getDiscoverCount() >= 2);
     Assert.assertTrue(testBatchPushSource.getDiscoverCount() <= 3);
+    batchSourceExecutor.close();
+    Assert.assertEquals(testBatchPushSource.getCloseCount(), 1);
   }
 }