Make QtQuickView stylable

Why?

Would save some (few) code lines from .java or .kt but would perhaps be familiar and preferred for Android workflow developer

What?

Add support for adding the QtQuickView from the layout xml file, instead of just programmatically. Need to add a styleable.xml resource to make it possible, and a way to provide that xml resource to the Android project. Note, having androiddeployqt add it like the rest of the xml resources is probably not enough, as this xml should be present before building the app.

Note, also need to add some public constructors to handle the styleable attributes, so changes to public APIs are required.

Who?

Team, needs FF reviews for API and .xml mechanism ready before API