Fix map assertion in TestLazyMap

`org.testng.Assert.assertEquals(Map, Map)` does not really check  map
equality when the actual map contains null values.

Migrate to AssertJ and fix the test.

plugin/trino-hive/src/test/java/io/trino/plugin/hive/util/TestLazyMap.java

@@ -28,7 +28,7 @@
 import static org.apache.hadoop.hive.serde2.lazy.LazyFactory.createLazyObject;
 import static org.apache.hadoop.hive.serde2.lazy.objectinspector.LazyObjectInspectorFactory.getLazySimpleMapObjectInspector;
 import static org.apache.hadoop.hive.serde2.lazy.objectinspector.primitive.LazyPrimitiveObjectInspectorFactory.getLazyStringObjectInspector;
-import static org.testng.Assert.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 public class TestLazyMap
 {
@@ -45,7 +45,7 @@ public void test()
         assertMapDecode("\\N\u0003ignored\u0002\u0003", ImmutableMap.of(lazyString(""), lazyString("")));
 
         HashMap<Object, Object> expectedMap = new HashMap<>();
-        expectedMap.put("null", null);
+        expectedMap.put(lazyString("null"), null);
         assertMapDecode("\\N\u0003ignored\u0002null\u0003\\N", expectedMap);
     }
 
@@ -63,7 +63,7 @@ public static void assertMapDecode(String encodedMap, Map<? extends Object, ? ex
         lazyMap.init(newByteArrayRef(encodedMap), 0, encodedMap.length());
 
         Map<Object, Object> map = lazyMap.getMap();
-        assertEquals(map, expectedMap);
+        assertThat(map).isEqualTo(expectedMap);
     }
 
     private static LazyString lazyString(String string)