Convert RelatedLinkRestriction for work items to static data

What does this MR do and why?

The Work Item Related Link Restriction table is not a good candidate for a sharding key, and so the recommendation is to simply convert it to static data in order to deprecate reliance on that table. This MR seeks to do that. It is really only WorkItems::RelatedWorkItemLink that relies on this table at the moment.

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Related to #553478 (closed)