Use new `level?` methods for `Service`

What does this MR do?

Service#group_level? and Service#instance_level? methods were added in !59838 (merged) to complement the existing Service#project_level? method.

This MR makes wider use of these methods in an attempt to form a single way of asking the "level" of an integration.

#326079 (closed)

Does this MR meet the acceptance criteria?

Conformity

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  • I have not included a changelog entry because ~"feature::maintenance"
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