- limit missing headers results set to 100 so that extraction doesn't
excessively block delegation
- wrap checked headers functions in repository struct
- move storage repository to factory, to correspond with event
repository path
- remove unused files
- reformat sql
- remove line breaks in imports
libraries/shared; adjust omni test_helpers to drop and recreate
checked_headers table to avoid reaching 1600 column limit after repeated
tests (dropping columns doesn't actually remove them from contributing
to that limit)
