Fix component type update deleting unmanaged relationships

[saditya370]

Summary

• Bug: Updating a component type (e.g. adding properties or changing description) would silently delete all relationship definitions, even when the user didn't touch the relationships block. Reported by LandSure on provider v1.9.0 (GitLab #14723).
• Root cause: reconcileRelationships() ran unconditionally on every update and deleted any API-side relationship not found in the current plan. A nil/empty plan meant "delete everything."
• Fix: Added a guard to skip reconciliation when neither plan nor prior state has relationships. Changed the deletion loop to only delete relationships that were previously in Terraform state but removed from the new plan. Relationships created outside Terraform (e.g. via UI) are now left untouched.

Test plan

• TestReconcileRelationships_NilPlanNilState — no relationships in plan or state → no deletes
• TestReconcileRelationships_NilPlanWithState — user removes relationships block → deletes only what was in state
• TestReconcileRelationships_PlanMatchesAPI — no changes → updates only, no deletes
• TestReconcileRelationships_EmptyPlanNilState — empty map with nil state → no deletes
• TestReconcileRelationships_APIHasExtraNotInState — UI-created relationships → left untouched
• TestReconcileRelationships_RemoveOneKeepOne — partial removal → deletes one, updates other
• TestReconcileRelationships_AddNewRelationship — new relationship added → creates it, no deletes
• TestReconcileRelationships_RemoveAllFromState — explicit removal of all → deletes all from state
• TestReconcileRelationships_StateHasOneAPIHasExtraKeepBoth — TF manages one, UI created another → only updates TF-managed one
• All existing tests pass (go test ./opslevel/ — 12/12)
• Full build clean (go build ./...)

[andrewstillv15]

We have to add a changie before this gets merged