add expression support for organisation instance owner name

[HauklandJ]

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[ivarne]

A (few) shared test(s) https://github.com/Altinn/app-frontend-react/tree/main/src/features/expressions/shared-tests/functions/instanceContext would be nice :)

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
95.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[olemartinorg]

Nice! 🙌 This will also affect text resource variables, so the docs for that should be updated: https://docs.altinn.studio/nb/altinn-studio/reference/ux/texts/#datakilder