Introduce ClassKind#CLASS_OBJECT and ClassKind#isObject and usages.

Rename LazyClassDescriptor#onlyEnumEntries -> enumClassObjectInfo.
Determine ClassKind in JetClassInfo and JetObjectInfo constructor.
Remove complex constructor for enum entry in enum test.
Logic simplified in LazyClassMemberScope.
Minor refactorings.

compiler/testData/lazyResolve/descriptorRenderer/ClassObject.kt

@@ -4,4 +4,4 @@ trait TheTrait {
 }
 
 //internal trait TheTrait defined in root package
-//object defined in TheTrait
+//class object defined in TheTrait