Implement data source for ESA WorldCover 2021 data.

[favyen2]

Add WorldCover data source. It is a wrapper around LocalFiles that helps with downloading all of the zip files from ESA website.

Also:

• Made some adjustments to LocalFiles to improve performance (use open_rasterio_upath_reader) and not require config.data_source to be set when using LocalFiles programmatically.
• Update GeotiffRasterFormat to allow setting the filename where raster should be encoded in case it is being used separately from an rslearn dataset (this is used e.g. for populating Helios dataset).

[yawenzzzz]

LGTM! Thanks for adding the WorldCover data. Using LocalFile seems like a good approach for static data (large GeoTIFFs that don’t change frequently over time). We can process SRTM, the average DynamicWorld in a very similar way.