Check for duplicates across dictionaries (#1501)

* Check for duplicates across dictionaries

And no longer allow self-corrections within these checks (given we exclude them elsewhere already)

* Improve the "is an error itself in another dictionary file" logging

* Try @larsoner 's proposed improvement to global dictionary checking

* Fix the syntax error and I think fix the cross-dictionary detection

* Ensure we catch all the error cases

* ENH: Refactor

* Move chack back to rare

* Fix the substitution variables for an error

* Move wen back from rare to names

* Finish moving chack to rare

* Remove a few en-GB to en-US conversions from rare

Co-authored-by: Eric Larson <larson.eric.d@gmail.com>