Migrate X-ray off AvailableServices#purchased?

What does this MR do and why?

Migrates the deprecated X-ray implementation off AvailableServices#purchased?, which is being removed in Replace methods that check for AddOnPurchases (#542422 - closed)

We use a new Unit Primitive based Fulfillment finder on AddOnPurchase instead.

I also introduced exists_for_unit_primitive? as a convenience helper and to make it easier to stub out these calls. I migrated existing calls to find → any? to this method.

Not a user-facing change.

References

#542422 (closed)

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Related to #542422 (closed)