LtsWidgets: Qt6 API fixes complete

- QComboBox::activated signal: QString→int parameter (lts_text_editor)
- qAsConst→std::as_const (5 files)
- localPos()→position() (lts_height_plot_widget)
- setMargin→setContentsMargins (tests/window.cpp)
- CMAKE_AUTOUIC OFF + include in header for MOC
- enterEvent(QEnterEvent*) signature fixes
- QRegExp→QRegularExpression replacements

All LtsWidgets module files now Qt6-compatible.

qt6-after/qt6-migrated-legatus/Lts/Common/LtsWidgets/lts_drag_icon.cpp

@@ -153,7 +153,7 @@ void LtsDragIcon::initButton()
 
 
   QVBoxLayout *box = new QVBoxLayout(this);
-  box->setMargin(0);
+  box->setContentsMargins(0, 0, 0, 0);
   box->setSpacing(0);
   box->addWidget(m_toolButton);
 
@@ -471,7 +471,7 @@ QIcon LtsDragIcon::modifyIcon(const QIcon &icon)
   QPainter painter(&iconImage);
 
   painter.save();
-  painter.setRenderHints(QPainter::TextAntialiasing | QPainter::Antialiasing | QPainter::HighQualityAntialiasing | QPainter::SmoothPixmapTransform);
+  painter.setRenderHints(QPainter::TextAntialiasing | QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
   painter.setBrush(QColor("red"));
   painter.setPen(QPen(QColor("red"), 3));