core: add CPUQuotaPeriodSec=
    
    This new setting allows configuration of CFS period on the CPU cgroup, instead
    of using a hardcoded default of 100ms.
    
    Tested:
    - Legacy cgroup + Unified cgroup
    - systemctl set-property
    - systemctl show
    - Confirmed that the cgroup settings (such as cpu.cfs_period_ns) were set
      appropriately, including updating the CPU quota (cpu.cfs_quota_ns) when
      CPUQuotaPeriodSec= is updated.
    - Checked that clamping works properly when either period or (quota * period)
      are below the resolution of 1ms, or if period is above the max of 1s.
    
    (cherry picked from commit 10f28641115733c61754342d5dcbe70b083bea4b)
    
    Resolves: #1770379
    
    patch_name: 0398-core-add-CPUQuotaPeriodSec.patch
    present_in_specfile: true
    location_in_specfile: 398
    squash_commits: true