QDesignerContainerExtension need canAddWidget and canRemoveWidget in Qt6.3

[MCA4213]

I have built the solution on msvc 2022 + Qt6.3 and I have some notes:

replace qt5_wrap_cpp with qt6_wrap_cpp in cmake ;

All class that use QDesignerContainerExtension have errors (abstract class):
add bool canRemove(int index) const Q_DECL_OVERRIDE; and bool canAddWidget() const Q_DECL_OVERRIDE;

Thanks and sorry to write in english, I don't know chinese.

[czyt1988]

I will take time later to improve the designer plugin