Merge pull request #17427 from liewegas/wip-pg-num-limits

mon/OSDMonitor: implement cluster pg limit

Reviewed-by: Josh Durgin <jdurgin@redhat.com>

diff --cc PendingReleaseNotes
Simple merge

diff --cc src/common/options.cc
Simple merge

diff --cc src/mon/OSDMonitor.cc
Simple merge

diff --cc src/mon/OSDMonitor.h
Simple merge

diff --cc src/mon/PGMap.cc
Simple merge