monitoring: Fetch Icinga object properties lazily
monitoring: Adapt host and service classes to match their base class' interface
lib: Add `InvalidPropertyException'
monitoring/commands: Remove superseded command forms and command objects

refs #6593
monitoring/commands: Support 'DISABLE_NOTIFICATIONS_EXPIRE_TIME'

refs #6593
monitoring/commands: Add icon to the check now command form

refs #6593
monitoring/commands: Fix instance command forms code compliance

refs #6593
monitoring/commands: Fix object command forms code compliance

refs #6593
monitoring/commands: Re-add the changed identifier to object features

refs #6593
monitoring/commands: Support toggling instance features

refs #6593
monitoring/commands: Use the toggle instance features command form in the process controller

refs #6593