Providing a preset searchable list of countries

## User story

As a form administrator, I want an updated searchable list component for countries that I can add to my form, so I don't need to create and import a new component each time.

> Would it be possible to incorporate a list of countries into a form of text-entry validation, instead of having to create a searchable list with each form?

## Related
#5849
https://cds-snc.freshdesk.com/a/tickets/28696
https://cds-snc.freshdesk.com/a/tickets/22673
https://cds-snc.freshdesk.com/a/tickets/21214
https://cds-snc.freshdesk.com/a/tickets/19868
https://cds-snc.freshdesk.com/a/tickets/18236
https://cds-snc.freshdesk.com/a/tickets/26751

Start by reviewing related issue #5849 and the existing searchable-list and text-entry validation entry points in the Forms client. Compare the linked support requests to clarify the expected country data and behavior. Done means administrators can add an updated searchable country list without creating and importing a component for each form, with the relevant tests passing.

Written by the indexing model from the issue text.