Qt6 Migration: Merge latest Qt5 devel content and apply migration fixes

- Merged 292 changed files from dlbo snapshot
- Fixed IDL enum collisions (PortType, PdmEventType)
- Fixed Grantlee template for C++11 scoped enums
- Fixed CMake VERSION_GREATER syntax
- Added missing directories (THP, LtsRestClient, etc.)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Lts/Common/LtsPluginManager/lts_plugin_loader.h

@@ -49,6 +49,8 @@ enum class PluginType
   PROJECT,
   STYLE,
   SPECIAL, // TODO: rm
+  GUI_ELEMENT,
+
 };