partial implementation of forward-posting setup/hold timing constraints
refactor EventPool implementation into class template
Merge branch 'master' into prsim-timing-backannot
draft implementation of forward posting setup/hold checks, passes tests!
TODO: checkpoint preservation/restoring of active timing checks
started to save/checkpoint timing check information, need to refactor first
refactored timing_checker into own class
implemented active timing constraint checkpointing
force consistent use of NodeState::translate_value_to_char
leave PRSIM_FWD_POST_TIMING_CHECKS disabled for now, though it is working