[ingestion] Fix deserializePositionWithOffsetFallback to preserve symbolic positions

The deserializePositionWithOffsetFallback method was incorrectly treating
symbolic positions (EARLIEST, LATEST) as regular positions and comparing
their numeric offsets against the provided minimum offset. This caused
EARLIEST (numeric offset -1) to be replaced with an offset-based position
when the minimum offset was >= 0.

Added a guard to detect and preserve symbolic positions before performing
numeric offset comparison, ensuring they are returned as-is regardless of
the minimum offset parameter.

This fix resolves the failing testDeserializePositionWithOffsetFallback
test in LeaderFollowerStoreIngestionTaskTest.

Test: ./gradlew :clients:da-vinci-client:test --tests "com.linkedin.davinci.kafka.consumer.LeaderFollowerStoreIngestionTaskTest"

Author: sushantmane

clients/da-vinci-client/src/main/java/com/linkedin/davinci/kafka/consumer/StoreIngestionTask.java

@@ -5179,6 +5179,12 @@ PubSubPosition deserializePositionWithOffsetFallback(
 
     try {
       final PubSubPosition position = pubSubPositionDeserializer.toPosition(wireFormatBytes);
+
+      // Symbolic positions (EARLIEST, LATEST) should always be returned as-is
+      if (position == PubSubSymbolicPosition.EARLIEST || position == PubSubSymbolicPosition.LATEST) {
+        return position;
+      }
+
       // Guard against regressions: honor the caller-provided minimum offset.
       if (position.getNumericOffset() < offset) {
         String context = String.format(" for: %s/%s", topicPartition, versionTopic);