ExtensionSystem: Move away from QList

Qt 6 API will move away from it.
Use QVector for API and some std container for internal things.

Change-Id: Iff14d48a47d5ac52ade875d9c8c84ad8a4f577d8
Reviewed-by: hjk <hjk@qt.io>

src/plugins/clangtools/clangtoolsplugin.cpp

@@ -132,9 +132,9 @@ bool ClangToolsPlugin::initialize(const QStringList &arguments, QString *errorSt
     return true;
 }
 
-QList<QObject *> ClangToolsPlugin::createTestObjects() const
+QVector<QObject *> ClangToolsPlugin::createTestObjects() const
 {
-    QList<QObject *> tests;
+    QVector<QObject *> tests;
 #ifdef WITH_TESTS
     tests << new PreconfiguredSessionTests;
     tests << new ClangToolsUnitTests;