refs #18333 [finc] refactoring of linked records

* remove addFincIdToRecord
* introduce searchRelatedRecords instead
* introduce getLinkedKxpRecord for multiple record linking functions
* move getRelatedRecords funcionality to getAdditionals
* show more Online Editions in holdings tab
** extend getAdditionals by note (MARC subfield $n)
** also show link if $n === 'Online-Ausgabe"
* detail view
** only show actually linked records if present
** show more elaborate label for related records
* refactor getHierarchyParentID
** reuse getRelatedKxpRecord