Provide consistent tooling for submodules within the monorepo

Provide consistent tooling for submodules within the monorepo (e.g. linting and test execution over all subdirectories)

• Invest into infrastructure
• Implement sth so we would not need to make any changes to the ci after adding tests in subdirectories
• Probably create and call makefiles in subdirectories which run all the testing for each of the subdirectories