Fix build failures with Java 16.

A few test that used reflection to access the actual SQL executed by a Query object failed with `java.lang.reflect.InaccessibleObjectException: Unable to make field protected java.lang.reflect.InvocationHandler java.lang.reflect.Proxy.h accessible: module java.base does not "opens java.lang.reflect" to unnamed module 1b9e1916`.
This change replaces the reflection used by a proper call to `unwrap`.

Original pull request #2231

Author: schauder

src/test/java/org/springframework/data/jpa/repository/query/PartTreeJpaQueryIntegrationTests.java

@@ -33,10 +33,10 @@
 import javax.persistence.TemporalType;
 
 import org.hibernate.Version;
+import org.hibernate.query.internal.QueryImpl;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
-
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
@@ -107,11 +107,11 @@ void recreatesQueryIfNullValueIsGiven() throws Exception {
 
 		Query query = jpaQuery.createQuery((getAccessor(queryMethod, new Object[] { "Matthews", PageRequest.of(0, 1) })));
 
-		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY))).endsWith("firstname=:param0");
+		assertThat(HibernateUtils.getHibernateQuery(query.unwrap(QueryImpl.class))).endsWith("firstname=:param0");
 
 		query = jpaQuery.createQuery((getAccessor(queryMethod, new Object[] { null, PageRequest.of(0, 1) })));
 
-		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY))).endsWith("firstname is null");
+		assertThat(HibernateUtils.getHibernateQuery(query.unwrap(QueryImpl.class))).endsWith("firstname is null");
 	}
 
 	@Test // DATAJPA-920
@@ -133,7 +133,7 @@ void shouldSelectAliasedIdForExistsProjectionQueries() throws Exception {
 
 		Query query = jpaQuery.createQuery((getAccessor(queryMethod, new Object[] { "Matthews" })));
 
-		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY))).contains(".id from User as");
+		assertThat(HibernateUtils.getHibernateQuery(query.unwrap(QueryImpl.class))).contains(".id from User as");
 	}
 
 	@Test // DATAJPA-1074
@@ -144,7 +144,7 @@ void isEmptyCollection() throws Exception {
 
 		Query query = jpaQuery.createQuery((getAccessor(queryMethod, new Object[] {})));
 
-		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY))).endsWith("roles is empty");
+		assertThat(HibernateUtils.getHibernateQuery(query.unwrap(QueryImpl.class))).endsWith("roles is empty");
 	}
 
 	@Test // DATAJPA-1074
@@ -155,7 +155,7 @@ void isNotEmptyCollection() throws Exception {
 
 		Query query = jpaQuery.createQuery((getAccessor(queryMethod, new Object[] {})));
 
-		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY))).endsWith("roles is not empty");
+		assertThat(HibernateUtils.getHibernateQuery(query.unwrap(QueryImpl.class))).endsWith("roles is not empty");
 	}
 
 	@Test // DATAJPA-1074