What happened:
The excessive `onSpriteLoaded()` notifications were caused by the trick inside `OnlineFileRequest::completed()` implemenation,
which causes receving of two file source updates pointing to the *same* data in case the network response is `notModified` and
the local storage has the sprite sheet already stored inside.
In the SpriteLoader` implementation, it resulted in 2 extra `parseSprite()` calls and 2 extra `onSpriteLoaded()` notifications.
Then, the excessive `onSpriteLoaded()` notifications affected style images and all the unnecessarily added image dupes (btw,
the amount of these dupes `= 2 * number of style images`) were treated by the `RenderOrchestrator` as *updated* images.
Further, `RenderOrchestrator` called `ImageManager::updateImage()` for the updated images and the `ImageManager` populated the
`updatedImageVersions` map.
Finally, at every frame all the geometry tiles iterated through the `updatedImageVersions` to check whether their uploaded
textures needed patching.
All the mentioned above had a negative performance impact.
The fix:
Now, `SpriteLoader` sends `onSpriteLoaded()` notifications only if the data in the file source response is different comparing
to the existing one.
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