Consider moving RasterTiler class to the viz-workflow repo

[robyngit]

Consider moving the entire RasterTiler.py class to the viz-workflow repo, and remove it from this repo. Advantages:

• Stay consistent with viz-3dtiles repo
• pdgstaging not a dependency
• keep viz-raster generic (just creates rasters from vectors, independent from staging)

This would also make it easy to, for example, read in a staged vector file as a geodataframe only once, deduplicate only once, then pass that geodataframe to be converted to both 3dtiles and rasters. All of this could be coordinated in the viz-workflow repo.

See discussion here