scaling issues in map.qml example

qtdeclarative/examples/quick/pointerhandlers/map.qml easily gets into a state where it tries to re-render the SVG file at "too large" a size, but it's not clear how large is too large: the image simply disappears if you exceed whatever limit that is. And then, after it tried and failed to render it at 50000 pixels wide or whatever, attempting to pinch it back down to reasonable size does not work immediately: you often need to try a couple of times before it begins rendering again.

This is related to PDF scaling, since the QML-implemented PDF viewing components use a similar strategy. All these things need to start using BoundaryRule properly, and we need to somehow expose the actual texture size limit that the GPU can handle, rather than using simple limits like 10x the original size or whatever.