Fix working with latest dask

[manthey]

See PR #1144; dask introduced a breaking change.

Superficially, my guess is that it fails to unpickle tiles correctly.

[manthey]

Specifically, this changes how the tiles are serialized and deserialized in dask. A tile (large_image.tilesource.tiledict.LazyTileDict) is a subclassed dictionary. In dask<2024.11 this serialized and deserialzes as a LazyTileDict. In recent dask, it deserializes as a dict.

[manthey]

There is now an issue in distributed for this problem: dask/distributed#8932