Various cleanups to QML file locations and related code
- kirigamistyle: Remove disfunctional Icon.qml file
Icon is a primitive type that is not overridable so this file is never used. It also doesn't make sense since it uses Kirigami.Icon internally so if it would actually load it'd end up in a weird loading loop.
- declarativeimports/core: Remove manual Qt resource handling
Instead rely on the Qt module code and load DefaultToolTip from the actual module.
- sharedqmlengine: Allowing loading by module/type rather than URL
This was added upstream to support proper QML modules and generally leads to nicer code that doesn't need to know file layout, so extend that ability to SharedQmlEngine.
- sharedqmlengine: Use unique_ptr for storing internal component
This removes the need for a bunch of manual memory handling.
- plasmaquick: Remove obsolete resources file
With the background moved into the core plugin there is no need for manual resource handling here.
- quick/dialogbackground: Ensure we delete the SVG item
It is rather unclear how ownership is here and when the SVG is deleted. So make sure to request deletion if the background object is deleted.
- Move DialogBackground into core QML plugin
This allows it to be processed by all the new tooling around QML modules, including converting the simple bindings in this file to C++. Since we can now specify what type to load in a Component by module/type name this also makes the loading code nicer.