Feat pb 1578 package distribution

[msom]

This PR

• Renames to stac_harvest command to stac_sync to better match the other command.
• Adds a _legacy_imported flag to the package distributions to keep track of imported datasets, similar to the bod_sync.
• Adds support for importing unmanaged package distributions. These are the packages found on the root page of data.geo.admin.ch but not in STAC.
• Adds a default dataset argument to be used when no matching dataset is found for a package distribution.

[msom]

@benschs I also added a provider filter for the package distributions