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/libs/utils/projectintropage.cpp

@@ -195,6 +195,11 @@ bool ProjectIntroPage::validate()
     return false;
 }
 
+void ProjectIntroPage::fieldsUpdated()
+{
+    slotChanged();
+}
+
 void ProjectIntroPage::slotChanged()
 {
     const bool newComplete = validate();
@@ -286,6 +291,8 @@ void ProjectIntroPage::displayStatusMessage(InfoLabel::InfoType t, const QString
 {
     d->m_ui.stateLabel->setType(t);
     d->m_ui.stateLabel->setText(s);
+
+    emit statusMessageChanged(t, s);
 }
 
 void ProjectIntroPage::hideStatusLabel()