chore: make sure to include the new row key in row merging errors (googleapis#2046)

* chore: make sure to include the new row key in row merging errors

Change-Id: Ieebc425d359a426d24c1ed69d0093e97635bd742

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: igorbernstein2

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/readrows/StateMachine.java

@@ -277,6 +277,10 @@ State handleLastScannedRow(ByteString rowKey) {
 
         @Override
         State handleChunk(CellChunk chunk) {
+          // Make sure to populate the rowKey before validations so that validation failures include
+          // the new key
+          rowKey = chunk.getRowKey();
+
           validate(!chunk.getResetRow(), "AWAITING_NEW_ROW: can't reset");
           validate(!chunk.getRowKey().isEmpty(), "AWAITING_NEW_ROW: rowKey missing");
           validate(chunk.hasFamilyName(), "AWAITING_NEW_ROW: family missing");