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/tests/window.cpp

@@ -17,7 +17,7 @@ Window::Window(QWidget *parent)
 
   QHBoxLayout *lay = new QHBoxLayout;
 
-  lay->setMargin(0);
+  lay->setContentsMargins(0, 0, 0, 0);
   //lay->setSizeConstraint(QLayout::SetMinimumSize);