Add activation priorities for config object types

Add activation priorities for config object types

This patch ensures that specific configuration types
are pre-activated and post-activated. In general,
logging is first, then common configuration objects
like host/service, downtimes, etc.
In the end, all features are activated after to ensure
that notifications are only sent once downtimes are applied.
A similar thing happens for starting with checks too early.
The ApiListener feature runs first to allow cluster connections
at first glance.

fixes #6057
fixes #6231