Add COG-style multiscale utilities for GeoZarr

- Implement functions to create Cloud Optimized GeoTIFF (COG) style overview levels.
- Calculate overview levels based on native dimensions and downsampling logic.
- Create overview templates maintaining native CRS and spatial attributes.
- Populate overview arrays with downsampled data using numpy methods.
- Verify coordinates and CRS in overview levels.
- Plot overview levels using xarray's native plotting capabilities.

Author: emmanuelmathot

docs/examples/06_multiscales_as_WebMercatorQuad_EOPFZarrV3.ipynb

@@ -81,3 +81,6 @@ geoviews = "*"
 
 [dependency-groups]
 test = ["pytest"]
+
+[project.entry-points."xarray.chunkmanagers"]
+dask = "xarray.namedarray.daskmanager:DaskManager"