Chore/Create mock solution for reusability of unittest mocks and data

[allinox]

Description

This PR rips the Mock and Mock-data parts out of the test project and establishes a new project solution 'Mocks'. Mocks is then used by Tests for unit testing as previously, but can now also be reused during runtime in Dev whenever UseMockData is set in appsettings.Development.json

This can be benefitial when developing frontend code for backend endpoints that are not yet created, or are for some reason unavailable or broken. It also lessens the need for setup (souch as Database setup and policy files in Azure) before a developer can begin coding in frontend.

Related Issue(s)

• BFF: Create new Mock project for use both in unit tests and runtime mocking #445

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)

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
1 Vulnerability
0 Security Hotspots
47 Code Smells

82.7% Coverage
0.0% Duplication

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