Make additional changes in the QtCreator side required for QDS new project dialog

* We need to use the CheckBox field to set the checked state of fields
  (TargetQtVersion, Use as default project location).
* When the validation of the Project Name or Project Location fails, we
  need a way to be notified of what went wrong. We also need a way to
  force the project intro page to execute the validation of those fields
  whenever we need (i.e. when the user types into our QML TextField
  controls)

Also, add a warning on loading wizards: whenever a wizard.json file
cannot be parsed, we should issue a qWarning(), so that we can more
easily notice when something went wrong.

Task-number: QDS-4490
Change-Id: I7cfa61b4e43d731db9d0679e093e723d947b60c0
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp

@@ -956,6 +956,15 @@ void CheckBoxField::setup(JsonFieldPage *page, const QString &name)
     });
 }
 
+void CheckBoxField::setChecked(bool value)
+{
+    auto w = qobject_cast<QCheckBox *>(widget());
+    QTC_ASSERT(w, return);
+
+    w->setChecked(value);
+    w->clicked(value);
+}
+
 bool CheckBoxField::validate(MacroExpander *expander, QString *message)
 {
     if (!JsonFieldPage::Field::validate(expander, message))