Add a build and run label to the tests referencing the project name

When combining multiple modules, using add_subdirectory or FetchContent, e.g., in the context of super-builds, all targets and all tests are combined in the build_tests custom target. In the MR I introduce another custom target build_<module>_tests that allows to compile test targets from a single module only. Additionally, a test label is added to allow executing only those tests.