"collection" vs "collection_name" potential confusion.

[nbarlowATI]

In the pyveg_pipeline code, we currently have Sequences being called e.g. "Sentinel2", and their parameter collection_name being e.g. "COPERNICUS/S2".
Personally I feel like "COPERNICUS/S2" should be the collection, and "Sentinel2" should be collection_name.

However, making this change now would affect the metadata for all data already downloaded/processed.