move contents larger than current injection limit to separate object storage

Due to legacy reasons we have imported (from the Antelink archive) contents in our object storage that are individually larger than the current maximum size limit (100 MB) used by loaders that are currently in production. That creates inconsistencies as well as performance problems for very large objects, like some DVD ISO images. We want to move objects that are larger than the current limit to a separate object storage, and move them from the content table to the content_missing table in the DB, so that all their metadata are retained.

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Migrated from T809 (view on Phabricator)