tests: rework the code fuzzing journald
    
    This should make it easier to add a new fuzzer without a lot of
    duplication.
    
    (cherry picked from commit b1bd453f36b9428b6bf9feba31fa0a2b36143e9c)
    
    Resolves: #1696224
    
    patch_name: 0143-tests-rework-the-code-fuzzing-journald.patch
    present_in_specfile: true
    location_in_specfile: 143
    squash_commits: true