Extend list-modules action output

[DavidePrincipi]

PR summary:

1. Add two new fields to the module repository schema:
   • terms_url
   • upstream_name
2. Add new computed fields to list-module output:
   • certification_level
   • rootfull
3. In the list-module updates array, add a new attribute for instances that have an available testing release update: testing_update

See individual commit and JSON schema descriptions for full details.

Refs NethServer/dev#6956