Improve failed save handling

Small bug fixes

PHP8.2 Support

Add AllowDynamicProperties attribute to Event class to silence PHP8.2 deprecation notice
Various small improvements

Drop the CPU

Replaced React\Filesystem with a Child Process based offload for save state saving, a huge reduction in CPU time and reduced external dependancies
Opcache statistics are now visible in the administration interface

Heartbeat delay

Allow heartbeat to have a delayed startup.

Heartbeat

Add a configurable realtime heartbeat event to be injected into a running engine

Failed Action Recovery

Implement failed action recovery on restart by replaying actions before starting up any input processes. This could be failed actions due to engine failure (killed by OOM or hardware failure) or due to a misconfiguration or resource unavailability (eg database offline)

Add in additional metrics for tracking how long it takes to do the async save time and size of the save state file, exposed via the management server.

Add $essential flag to input processes to shutdown the engine if the process fails to start or shutdowns cleanly

Full Changelog: v0.4.4...v0.5

Logger

Add a PSR3 compatible logging facility for processes to log back centrally to the scheduler

Cron

Adds a Cron like rule to execute actions or generate events based on a cron expression schedule, or engine startup or shutdown.
Add in logic to restart failed input processes

Remove debug text

Remove debug text from SysInfo

Improved memory limit detection

Use additional inputs of physical/vm memory and cgroups limits in calculating the amount of memory available to the scheduler.