identifiers.parse_swhid: Make SWHIDs with whitespaces invalid
This should address the last concern demonstrated during our deposit discussion [1]
when the following stack of diffs lands, this probably needs an email on swh-devel as a heads-up.
"swh.model.identifiers.parse_swhid is getting more strict. This might notify you on invalid SWHIDs when it did not before"
Related to #2769 (closed) Depends on !255 (closed)
Test Plan
tox
Migrated from D4462 (view on Phabricator)