Add language to IDataProcessor and as an optional query param to apis

[ivarne]

In data processing it is sometimes valuable to know the language the user currently is showing in the schema.

At least two cases comes to mind:

1. Saving the language to the data model for knowing the language to use for potential follow up with the reportee
2. Updating presentation values with correct language (Uke 2 2023 vs Week 2 2023).

This PR also adds a Roslyn rewrite to fix the interface.

Description

Related Issue(s)

• Frontend language change should inform the backend #16
• (Alternative solution for) Expose used language in a way that allows putting into the data model app-frontend-react#1661

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)
• All tests run green

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[tjololo]

Looks good, we could remove some replicated code though

[sonarcloud]

Quality Gate passed

The SonarCloud Quality Gate passed, but some issues were introduced.

1 New issue
0 Security Hotspots
78.6% Coverage on New Code
2.6% Duplication on New Code

See analysis details on SonarCloud