Move from Karma Testrunner to Web Test Runner

[dsilhavy]

Description

The Karma Testrunner is outdated:

• https://github.com/karma-runner/karma

Karma is deprecated and is not accepting new features or general bug fixes

We should move to a testrunner that is still maintained e.g. Web Test Runner. This includes the execution of our unit tests and the execution of the functional Karma testsuite.

[dsilhavy]

Another popular option is https://vitest.dev/. This could imply that we move to https://vite.dev/ and replace Webpack