variable geometry support, plotting, WKB IO

[martinfleis]

This is a bit of a best but it got too interlinked that breaking it apart would be pain. It has came to live during a week-long workshop with @loreabad6 and I needed to use the time with her to get the functionality in.

So, this PR is a quite a milestone for Xvec as it:

1. adds support for variable geometry (shapely geometry as data in the array, not only as coordinates). Think about moving geometries, time evolving (e.g. glaciers) and so on.
2. add support to summarise variable geometry using GeometryIndex
3. add support for plotting of all kinds of data cubes
4. add encoding and decoding to WKB that supports Zarr serialisation of variable geometry
5. expands zonal stats so it can be used with variable geometry on input

Tests are still mostly missing as is documentation, so WIP.

@benbovy to store the CRS of variable geometry, I opted for xproj as it does precisely what I needed. Is it a good idea? I made sure we don't depend on it yet.

[martinfleis]

If you want to see the stuff in action, here:

• https://xvec--98.org.readthedocs.build/en/98/summary_geometry.html
• https://xvec--98.org.readthedocs.build/en/98/plotting.html and https://xvec--98.org.readthedocs.build/en/98/plotting-temp.html
• https://xvec--98.org.readthedocs.build/en/98/io.html#zarr-and-well-known-binary
• and updated intro to account for variable geometry https://xvec--98.org.readthedocs.build/en/98/intro.html

[benbovy]

@benbovy to store the CRS of variable geometry, I opted for xproj as it does precisely what I needed. Is it a good idea? I made sure we don't depend on it yet.

Yes I think it is a good idea :-) !

I haven't looked closely into this massive PR, though. From what I see you use the .proj.crs property to access the CRS, which assumes a unique CRS for the whole Dataset or DataArray.

BTW I plan to submit another Xvec PR in order to make xvec.GeometryIndex CRS-aware from xproj's point of view, which does not require depending on xproj either. One possible caveat is that if xproj finds several GeometryIndex coordinates with different CRSs in the DataArray / Dataset, .proj.crs will raise an error.

In CF conventions any data variable having (horizontal) spatial dimensions can be linked to a spatial reference (scalar) variable via its grid_mapping attribute, but xproj does not handle that yet (I opened benbovy/xproj#21).

[benbovy]

This PR looks amazing!

[codecov]

Codecov Report

Attention: Patch coverage is 40.98361% with 144 lines in your changes missing coverage. Please review.

Project coverage is 80.91%. Comparing base (66b541b) to head (4df37db).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
xvec/plotting.py	13.67%	101 Missing ⚠️
xvec/zonal.py	6.25%	30 Missing ⚠️
xvec/accessor.py	86.31%	13 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #98       +/-   ##
===========================================
- Coverage   98.70%   80.91%   -17.80%     
===========================================
  Files           4        5        +1     
  Lines         540      791      +251     
===========================================
+ Hits          533      640      +107     
- Misses          7      151      +144     

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