[HUDI-4039] Make sure all builtin KeyGenerators properly implement Spark specific APIs (#5523)

This set of changes makes sure that all builtin KeyGenerators properly implement Spark-specific APIs in a performant way (minimizing key-generators overhead)

hudi-common/src/test/java/org/apache/hudi/common/util/TestParquetUtils.java

@@ -259,7 +259,7 @@ public class TestParquetUtils extends HoodieCommonTestHarness {
     }
 
     @Override
-    public List<String> getRecordKeyFields() {
+    public List<String> getRecordKeyFieldNames() {
       return Arrays.asList(new String[]{recordKeyField});
     }