load_stac: avoid dependency on eo:bands

[jdries]

When loading our own netcdf metadata, I get: No band assets found in items; a band asset requires an "eo:bands" property with a "name". While the use of the name in eo:bands is relevant, all stac assets also have a default name, because assets in STAC are represented by a dictionary. Can we fall back to those names, if eo:bands is not present? I think that would make our load_stac less extension dependent.

[bossie]

Yes, I've been considering this as a best-effort approach. The implicit assumption then is that those are single band assets.

[soxofaan]

Maybe worth mentioning that in the python client we're also started to collect functionality to parse band information from stac:

• https://github.com/Open-EO/openeo-python-client/issues/527
• https://github.com/Open-EO/openeo-python-client/pull/548
• https://github.com/Open-EO/openeo-python-client/issues/553

We might want to consolidate efforts here