Move unit/integration test setup to shared module

What does this MR do and why?

This MR fixes and simplifies some issues with the frontend_integration test environment by splitting up the frontend/test_setup into a shared and unit-test specific module.

How to set up and validate locally

Run yarn run jest or yarn run jest:integration to confirm that both test suites still behave as expected.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.