MINOR : Fix possible flake in ShareConsumerTest:testConsumerCloseInGroupSequential (#19986)

*What*

- There was a possibility of a flake occurring in one of the tests in
`ShareConsumerTest` where we are not waiting for the assignment to be
received and synced before we start consuming on `poll()`.

- There should ideally be a `waitedPoll()` or a dedicated poll which
would trigger the reconcilation and updation of the assignment.

Scenario :

- We are doing 3 `polls` to receive 1500 records.

- On debugging, I noticed 1st poll always returned 0 records as this was
triggering reconcilation, the test passed locally as 2nd and 3rd polls
add up to give us 1500 records almost always (as 500 is a soft limit).
The test can fail if these 2 `polls` do not add up 1500. We need a
maximum
of 3 polls to receive 1500 records with `max.poll.records` set to 500.
- Now we have introduced a loop which would keep polling until we
receive the expected records and then close.

Reviewers: Andrew Schofield <aschofield@confluent.io>

clients/clients-integration-tests/src/test/java/org/apache/kafka/clients/consumer/ShareConsumerTest.java

@@ -1205,22 +1205,25 @@ public class ShareConsumerTest {
             int consumer1MessageCount = 0;
             int consumer2MessageCount = 0;
 
-            // Poll three times to receive records. The second poll acknowledges the records
-            // from the first poll, and so on. The third poll's records are not acknowledged
+            // Poll until we receive all the records. The second poll acknowledges the records
+            // from the first poll, and so on.
+            // The last poll's records are not acknowledged
             // because the consumer is closed, which makes the broker release the records fetched.
-            ConsumerRecords<byte[], byte[]> records1 = shareConsumer1.poll(Duration.ofMillis(5000));
-            consumer1MessageCount += records1.count();
-            int consumer1MessageCountA = records1.count();
-            records1 = shareConsumer1.poll(Duration.ofMillis(5000));
-            consumer1MessageCount += records1.count();
-            int consumer1MessageCountB = records1.count();
-            records1 = shareConsumer1.poll(Duration.ofMillis(5000));
-            int consumer1MessageCountC = records1.count();
-            assertEquals(totalMessages, consumer1MessageCountA + consumer1MessageCountB + consumer1MessageCountC);
-            shareConsumer1.close();
-
             int maxRetries = 10;
             int retries = 0;
+            int lastPollRecordCount = 0;
+            while (consumer1MessageCount < totalMessages && retries < maxRetries) {
+                lastPollRecordCount = shareConsumer1.poll(Duration.ofMillis(5000)).count();
+                consumer1MessageCount += lastPollRecordCount;
+                retries++;
+            }
+            assertEquals(totalMessages, consumer1MessageCount);
+            shareConsumer1.close();
+
+            // These records are released after the first consumer closes.
+            consumer1MessageCount -= lastPollRecordCount;
+
+            retries = 0;
             while (consumer1MessageCount + consumer2MessageCount < totalMessages && retries < maxRetries) {
                 ConsumerRecords<byte[], byte[]> records2 = shareConsumer2.poll(Duration.ofMillis(5000));
                 consumer2MessageCount += records2.count();