Ignore flapping state if flapping detection isn't enabled

[yhabteab]

The Icinga 2 Checkable flapping runtime attribute is always updated even when flapping detection is disabled and leads to false positives, causing Icinga Notifications to falsely suppress an incident. To prevent this, this PR additionally checks for the enable_flapping attribute of a checkable and globally for the IcingaApplication type.

And YES, I can safely use app as a json key because of this.

[2024-07-08 11:20:18 +0200] critical/config: Error: Validation failed for object 'my-app' of type 'IcingaApplication'; Attribute 'name': Application object must be named 'app'.
Location: in /Users/yhabteab/Workspace/icinga2/prefix/etc/icinga2/features-enabled/app.conf: 1:0-1:32
/Users/yhabteab/Workspace/icinga2/prefix/etc/icinga2/features-enabled/app.conf(1): object IcingaApplication "my-app" {}
                                                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/Users/yhabteab/Workspace/icinga2/prefix/etc/icinga2/features-enabled/app.conf(2): 
/Users/yhabteab/Workspace/icinga2/prefix/etc/icinga2/features-enabled/app.conf(3):