Try to run linter and unit test from top-level directory

Instead of starting a separate pipeline for each service we now just run
the linter and unit tests from the top-level directory. This allows us
to run the linter it with '--modules-download-mode vendor' and should also
reduce the resource usage.
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f