Werk #16466: introduce possibility to update discovered service labels

Prior to this werk, it was not possible to update only the discovered labels of a service. Updating those were tied to updating the identified parameters of the service. This werk introduces the option to update the discovered service labels only automatically as well as manually. The following changes were made to introduce this option as well for better visibility:

• Service discovery page: changed services due to a change in their labels are now listed under 'Changed services'. Service labels can be manually updated with dedicated actions targeting all changed services or a specific service
• Check_MK Discovery service: the service now accounts for changed services due to label changes. The state of the discovery service for such cases can also be configured
• Bulk discovery & Periodic service discovery: now have the option to update labels of changed services

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