Add xarray-sql support

[ahuang11]

Just a proof of concept integrating https://github.com/alxmrs/xarray-sql

import xarray as xr
ds = xr.tutorial.open_dataset('air_temperature')
ds.to_netcdf('air.nc')

lumen-ai serve air.nc

I wonder if this should be a lumen extension, like lumen-anndata. Part of me feels like it should be in core, so it works like hvplot.xarray, but at the same time, unsure about the limitations about the SQL & xarray.

I think if xarray-sql supported xarray-datatrees, then it's possible to rebuild AnndataSource on this since xarray is a generalized library supporting n-D dimension datasets.

[droumis]

verrrry interesting.. It would be worthwhile to scope out how well it could support anndata