ping-check-hook-task-5 Implement PingCheckMgr
Implement PingCheckMgr class per Ping Check design
https://gitlab.isc.org/isc-projects/kea/-/wikis/Designs/ping-check
When complete PingCheckMgr should be integrated with PingChannel and PingContextStore and use them to fulfill ping check requests, including contexts expiration management
It will not be integrated into hook callouts (i.e not loadable, configurable) nor decline leases. These steps are left to task 6.
depends on #3055 (closed)