feat: implement wasNull for BigQueryResultSet

Author: PhongChuong

google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryResultImpl.java

@@ -666,7 +666,7 @@ public Date getDate(String fieldName) throws SQLException {
             TimeUnit.DAYS.toMillis(
                 Long.valueOf(
                     dateInt)); // For example int 18993 represents 2022-01-01, converting time to
-                               // milli seconds
+        // milli seconds
         return new Date(dateInMillis);
       }
     }

google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/BigQueryResultImplTest.java

@@ -77,7 +77,7 @@ public class BigQueryResultImplTest {
   private static final String TIME = "20:21:22";
   private static final Time EXPECTED_TIME = Time.valueOf(LocalTime.of(20, 21, 22));
   private static final String DATE = "2020-01-21";
-  private static final int DATE_INT = 18283; // 2020-01-21
+  private static final int DATE_INT = 0;
   private static final Date EXPECTED_DATE = java.sql.Date.valueOf(DATE);
   private static final int BUFFER_SIZE = 10;