Add new class CoreSWHID as an alternative to SWHID/QualifiedSWHID
Following the discussion on #3034, we decided to replace SWHID with two or three classes:
- QualifiedSWHID to replace the existing SWHID (standard types + qualifiers)
- CoreSWHID, for "core SWHID" only (standard types + no qualifiers)
- ExtendedSWHID for internal use in Software Heritage (extra types + no qualifiers)
This commit adds the second one
Migrated from D5107 (view on Phabricator)