Fix J9ClassHasIdentity flag assignment

[AditiS11]

Set the J9ClassHasIdentity flag only if the class is
not a value class and not an interface.

Fixes the following failure in test/jdk/valhalla/valuetypes/ValueClassTest.java

[14:01:06.476] STARTED    ValueClassTest::testIsValueObjectCompatible 'testIsValueObjectCompatible()'
org.opentest4j.AssertionFailedError: interface: java.lang.Comparable ==> expected: <true> but was: <false>
	at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
	at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
	at org.junit.jupiter.api.AssertEquals.failNotEqual(AssertEquals.java:197)
	at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:188)
	at org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:1167)
	at ValueClassTest.isValueObjectCompatibleCase(ValueClassTest.java:63)
	at ValueClassTest.testIsValueObjectCompatible(ValueClassTest.java:51)
	at java.base/java.lang.reflect.Method.invoke(Method.java:571)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1604)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1604)

[theresa-m]

I think you can remove the interface check here. J9ROMCLASS_IS_VALUE is only true when an interface flag is not set.

[AditiS11]

J9ROMCLASS_IS_VALUE is false for interfaces. If I remove the interface check, J9ROMCLASS_IS_VALUE will return false for interfaces and enters the else if block and sets J9ClassHasIdentity flag for interfaces too.

[hangshao0]

In the original code, if Valhalla JDK is running on an older version of class file (e.g. Java 21), J9ClassHasIdentity is set on interface. With this change, J9ClassHasIdentity won't be set.

Have you checked the return value of java.lang.Class.isIdentity() with OpenJDK Valhalla build if given a interface compiled by Java 21 ?