HHH-13682 Enable extended bytecode enhancement in NaturalIdInUninitializedAssociationTest

This test accesses a field of an entity directly and expects it to be
automatically initialized; this cannot work without extended bytecode
enhancement.

This used to work with Java 8 bytecode, but only by chance. It seems
that Java 8 bytecode relies on "synthetic", static access methods
inserted by the compiler to access the fields of entities in this test:
any access to the field is done through this access method instead of
through a direct field access. Since we apply bytecode enhancement to
all methods of entities, this means that access to fields triggers
initialization, without any bytecode enhancement in the caller class.

I believe this is specific to nested classes, but couldn't find a
source. For reference, the bytecode of access methods looks like this:

  static int access$002(org.hibernate.test.bytecode.enhancement.lazy.NaturalIdInUninitializedAssociationTest$AnEntity, int);
    Code:
       0: aload_0
       1: iload_1
       2: dup_x1
       3: putfield      #3                  // Field id:I
       6: ireturn

  static org.hibernate.test.bytecode.enhancement.lazy.NaturalIdInUninitializedAssociationTest$EntityImmutableNaturalId access$102(org.hibernate.test.bytecode.enhancement.lazy.NaturalIdInUninitializedAssociationTest$AnEntity, org.hibernate.test.bytecode.enhancement.lazy.NaturalIdInUninitializedAssociationTest$EntityImmutableNaturalId);
    Code:
       0: aload_0
       1: aload_1
       2: dup_x1
       3: putfield      #2                  // Field entityImmutableNaturalId:Lorg/hibernate/test/bytecode/enhancement/lazy/NaturalIdInUninitializedAssociationTest$EntityImmutableNaturalId;
       6: areturn

With Java 11, however, access to fields of entities is done directly,
even for nested classes. So the access methods no longer exist, and we
don't get automatic initialization upon field access. We need extended
bytecode enhancement, like we would in any other case of field access
(in particular accessing fields of non-nested classes).

(cherry picked from commit 1060baf74b)

hibernate-core/src/test/java/org/hibernate/test/bytecode/enhancement/lazy/NaturalIdInUninitializedAssociationTest.java

@@ -39,7 +39,7 @@ import static org.junit.Assert.assertFalse;
 @SuppressWarnings({"unused", "WeakerAccess","ResultOfMethodCallIgnored"})
 @TestForIssue( jiraKey = "HHH-13607" )
 @RunWith( BytecodeEnhancerRunner.class )
-@EnhancementOptions( lazyLoading = true )
+@EnhancementOptions( lazyLoading = true, extendedEnhancement = true )
 public class NaturalIdInUninitializedAssociationTest extends BaseNonConfigCoreFunctionalTestCase {
 
 	@Test