Previously, cursors were initialized with a single ImageData, which
caused issues on systems with varying zoom levels, for example, cursors
were not scaled at all on Linux, or were blurrily auto-scaled on
Windows.

This commit introduces a new constructor for the Cursor class that
accepts an ImageDataProvider object instead of ImageData. This allows the code
instantiating the cursor to pass an imageDataProvider capable of providing
appropriately scaled image data based on the current zoom level.