Refactor: Move global target merging responsibility to checks

[lvlcn-t]

Is there an existing feature request for this?

• I have searched the existing issues

Problem Description

The global targets are injected to the checks config into their target field. This was ok for the target manager MVP but the checks will become more complex and not every check can implement a string slice as target field.

Solution Description

Add a dedicated global targets field to the checks config structs. This field can then be merged into the targets field by the check itself depending on its config implementation.

Who can address the issue?

Everyone

Additional Context

No response