Add a new trivial runtime-test which simply runs a no-op pipeline. This
is a fast, trivial test that simply verifies osbuild is properly setup
and accessible.
Remove the explicit no-op test from the CI, now that the test-suite has
it as well.
The idea is that source can themselves spawn other modules, esp.
new secrets modules. For this they need to know the library dir,
aka 'libdir' throughout the osbuild source. Therefore change the
SourceServer to directly get the library directory instead of
just the sub-directory to the sources. Then pass the library
directory to via the JSON API to the source.
Adjust all usage of the SourceServer, including the tests.
