Refactoring viewer to focus on Xarray

[banesullivan]

This refactors the viewer so that it is an xarray-focused 3D viewer instead of general Zarr data.

For #12 and #13

The viewer has users select a DataArray in an Xarray DataSet, then select the X, Y, Z, and Time coordinate arrays before generating a mesh that is shown in the viewer.

To do

• Add time slider
• Better handle errors if trying to build mesh when arrays are not selected
• Add level of detail selection option
• Add more examples (perhaps a cloud-hosted dataset)
  • add some to DKC and verify things work via URLs
• Add a URL field to specify the path/URL
• Drop down menu to select sample datasets

Nicities

• Disable XYZT selections when array is not chosen
• Add slider to scale Z axes (or all axes??)
• Improve the mesh updating/building so that it is more automatic
• Use GeoVista for global plotting (ref https://github.com/pyvista/pyvista-xarray/blob/main/examples/level_of_detail_geovista.py)

Requires:

• Add property setters to VTK Algorithm pyvista/pyvista-xarray#39
• Add vtkAlgorithm support to add_mesh for pipelining pyvista/pyvista#3318

[banesullivan]

Merging for deployment/demo. Further improvements will come later