tests: put fuzz_journald_processing_function in a .c file
    
    (cherry picked from commit 231dca5579cfba6175d19eee5347d693893fb5aa)
    
    Resolves: #1764560
    
    patch_name: 0252-tests-put-fuzz_journald_processing_function-in-a-.c-.patch
    present_in_specfile: true
    location_in_specfile: 252
    squash_commits: true