Improve country dropdown for the "country of origin" filter in the advanced search for works.

This merge request implements the type-to-select functionality for the Country of Origin dropdown in the advanced search for works.

I reused the existing JavaScript logic from the Nationality filter (Task: T393278).

I integrated the functionality into the Country of Origin dropdown to enable quick text-based selection.

I verified that the feature works consistently with the Nationality dropdown.

Go to Advanced Search → Country of Origin.

Start typing a country name — the list should filter automatically.