fix(oncall): make labels/dynamic_labels order-insensitive

[sidharth-chauhan]

This PR fixes #2169.

The labels and dynamic_labels fields for grafana_oncall_integration were previously treated as lists, making Terraform detect diffs when only the order of labels changed. Since the OnCall API does not treat label order as significant, this caused unnecessary perma-diffs.

Changes

• Updated schema definitions for labels and dynamic_labels to use TypeSet instead of TypeList.
• Adjusted expand/flatten helpers for labels to support the new schema.
• Updated acceptance tests to validate label handling.
• Updated documentation examples to reflect the new labels and dynamic_labels format.

Outcome

Terraform will now treat labels and dynamic_labels as order-insensitive, preventing diffs when only their order changes.

Notes

• All local unit tests pass.
• Acceptance tests skipped locally (no Grafana Cloud credentials available). These will run in CI.

[sidharth-chauhan]

Hi @Ferril @willgallego-grafana, I’m following up on this PR to check if there’s anything else needed from my side or if I should wait for workflow approval and your review. Thanks for your time.

[sidharth-chauhan]

I’ve rebased the branch as suggested. Some acceptance tests are failing, but they don’t seem related to the change here. Please let me know if I should investigate this further or if they need to be rerun.
@stephan-rayner