Expand organisation lookup to support search by name

### Description

By allowing search by organisation name, rather than only organisation number, the forms would be more user friendly

Open api from brreg for [enhetsregister søk](https://data.brreg.no/enhetsregisteret/api/dokumentasjon/no/index.html#tag/Enheter/operation/hentEnheter)

### Additional Information

Mattilsynet wants this feature:
https://altinn.slack.com/archives/C02EJ9HKQA3/p1733839882324139

Start by locating the existing organisation-number lookup in the TypeScript/React form components, then read the linked Brønnøysund Register Centre enhetsregister search API documentation. Done means the organisation lookup accepts a name as well as an organisation number and the forms can use the resulting search data; the issue does not name specific files or tests.

Written by the indexing model from the issue text.