`load_stac`: possible improvements

[clausmichele]

Currently load_stac relies on the stackstac library, which works fine until we try to load more complex types of STAC objects.

As far as I am aware, current limitations of stackstac are:

• Can load only single band COGs: multi-band geoTIFFs are not supported
• Can't load STAC based on netCDF data
• Always load the data as Float64: https://github.com/gjoseph92/stackstac/issues/91
• Can produce a shift in the data: https://github.com/gjoseph92/stackstac/issues/207

This limits the functionality of the implemented process. I will investigate the possible switch to either:

• odc-stac: regularly maintained and updated
  • Currently doesn't handle scale and offset automatically: https://github.com/opendatacube/odc-stac/issues/55
• xpystac: based on both stackstac and odc-stac

WIP here: https://github.com/clausmichele/openeo-processes-dask/tree/feature/load_stac_odc