core: implement per unit journal rate limiting
    
    Add LogRateLimitIntervalSec= and LogRateLimitBurst= options for
    services. If provided, these values get passed to the journald
    client context, and those values are used in the rate limiting
    function in the journal over the the journald.conf values.
    
    Part of #10230
    
    (cherry picked from commit 90fc172e191f44979005a524521112f2bd1ff21b)
    
    Resolves: #1719577
    
    patch_name: 0234-core-implement-per-unit-journal-rate-limiting.patch
    present_in_specfile: true
    location_in_specfile: 234
    squash_commits: true