Migrate QML integration to modern QML

[narnaud]

This seems a not so easy tasks:

• Use macro like QML_ELEMENT, QML_SINGLETON
• Remove code to integrate the singleton
• Add necessary CMake Qt macros

But if I understand, it would remove some code, particularly in ScriptRunner, but also we won't have to handle Q_DECLARE_METATYPE...

[LeonMatthesKDAB]

We may want to do this before 1.0? As it may involve slight breaking changes to the resulting script code? 🤔

[LeonMatthesKDAB]

@ahayzen-kdab This is done now isn't it?
Edit: Nevermind, I thought this issue was on the CXX-Qt repo, as it was added to the CXX-Qt 1.0 project.
I've removed the issue from the project.