Tile creation rollback

This update simply adds a rollback on how tiles were computed for cellpose.

When QuPath 0.4.1 came out, the logic of the tiles was rewritted based on the StarDist Extension, which would force tiles to be a particular size, with optional padding. In our case, this tended to create tiles that were coering way more image space than necessary, creating large overhead.

So with this update, we have reverted back to the older way of doing it.

This should have no change, or perhaps very minor changes in the global normalization numbers and in cellpose normalization, because of the change in tile size and thus contents.