Splitting / parsing Landmark crosswalks

[bherr2]

Like 3D ref organs, there is a central crosswalk that needs split out to Landmarks when there are updates

[bherr2]

Code here (https://github.com/hubmapconsortium/hra-do-processor/blob/main/src/migration/ccf-landmarks/migrate.js#L37) can be adapted to work like https://github.com/hubmapconsortium/hra-do-processor/blob/main/src/update-ref-organ-crosswalk.js