Use tiled rendering for Canvas

[M4rtinK]

Tiled rendering might help with Canvas rendering rendering performance, especially for long routes as only the currently visible tiles would need to be drawn, not the whole route. This might also help with not blocking the rendering thread in case we can't get threaded rendering working.

[M4rtinK]

Looks like tiled canvas rendering was deprecated in Qt 5.7 - not that probably ever really worked or was documented in a usable manner.