Fix entity refresh for entities that have not been migrated

[jhrozek]

Summary

• Add a setter for properties - Adds a utility function to set a property so that we don't have to construct a map to construct properties to merge properties.
• Derive the name property from entity name for entities that have not migrated fully - We have entities in the database that have an entity instance, but no corresponding property because they have not been migrated properly. In that case, we can't use properties to refresh the entity because the properties are not there. The entity itself has a name, though, so let's use it to backfill the name property so that the properties object can always be used to refresh the rest.
• Improve error message - This would actually tell us what entity failed to refresh

Change Type

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

unit tests

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 52.865% (+0.1%) from 52.75%
when pulling 34db5a6 on jhrozek:fix_entity_lookup
into 2056a62 on stacklok:main.