assets/webapp-utils: Add lowercase validator for core SWHIDs
When entering a SWHID in a search input, check its core part is in lowercase and do not validate the form if it is not.
An error message clearly indicating that core SWHID should be in lowercase will then be displayed.
Nevertheless, core SWHID with uppercase chars in it will still be automatically fixed when provided to its resolve URL /
Related to T3298
Migrated from D5655 (view on Phabricator)