Add QC checks to ensure that proxy merges from DO, OMIM and ORDO are …

…documented (#6248)

* Create qc-proxy-merge-missing-preferred.sparql

* update xref

* revise syn scope, xref scope

* fix xref

* fix xref

* fix xrefs

* deprecate syn

* add comments and remove mapping

* add tag

* add preferred external

* move xref

* revise xref

* add pref ex

* revise xef

* fix xref

* revise xref

* revise xref

* fix xref

* revise xref

* revised xref

* revise xref

* revise xref

* revise xref

* Update qc-proxy-merge-missing-preferred.sparql

* Update qc-proxy-merge-missing-preferred.sparql

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Co-authored-by: Nicole Vasilevsky <[email protected]>