Support 5.x style composite types in qmltypes files

In Qt6 we don't want those anymore, but it's easy enough to support them
for now.

Task-number: QTBUG-87164
Change-Id: I2a6cd1dd99f772d132f71575c9c5f4538a3dd0f0
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/qmlcompiler/qqmljsimporter.cpp

@@ -198,7 +198,7 @@ void QQmlJSImporter::processImport(
 
     for (auto it = import.objects.begin(); it != import.objects.end(); ++it) {
         const auto &val = it.value();
-        if (!val->isComposite()) // Otherwise we have already done it in localFile2ScopeTree()
+        if (val->baseType().isNull()) // Otherwise we have already done it in localFile2ScopeTree()
             val->resolveTypes(types->cppNames);
     }
 }

tests/auto/qml/qmllint/data/OldQmltypes/plugins.qmltypes

@@ -6,5 +6,6 @@ Module {
         prototype: "QQuickItem"
         exports: ["OldQmltypes/Frame 1.0"]
         exportMetaObjectRevisions: [0]
+        isComposite: true
     }
 }