Open icechunk with manifests array

[wachsylon]

We would need an IcechunkParser to modify things on xarray-level and store it again with references only (no data).

Best and thanks,
Fabi

[TomNicholas]

100%. We need a get_virtual_ref method to be implemented in Icechunk upstream. Then this should be easy - it's mostly the same as the existing ZarrParser

(See earth-mover/icechunk#104)