Required advanced AddressComponent should allow empty c/o

[torbjokv]

Describe the bug

An address is could still be valid and complete without c/o filled.

{
    "id": "haraldhjemmeadresse",
    "type": "AddressComponent",
    "textResourceBindings": {
        "title": "HaraldAdresseLedetekst"
    },
    "dataModelBindings": {
        "address": "Harald.Gateadresse",
        "zipCode": "Harald.Postnr",
        "postPlace": "Harald.Poststed",
        "careOf": "Harald.Co",
        "houseNumber": "Harald.Bolignummer"
    },
    "simplified": false,
    "readOnly": false,
    "required": true
}

To Reproduce

Steps to reproduce the behavior:

1. Add AddressComponent
2. Disable simplified
3. bind it to something
4. Set AddressComponent as required in FormLayout.json
5. Fill all fields except c/o filed
6. observe that validation fails

Expected behavior

I expect form to be valid without c/o

Screenshots

[altinnadmin]

If we created an address widget to replace the current AddressComponent, this would become trivial.

All we need is to get the horizontal layout support in #1515 shipped first 😃

[lvbachmann]

To be solved by Altinn/app-frontend-react#289 (as per suggestion by @altinnadmin).