This change renames directories in preparation for the great package
rename. The repository is now in a broken state because the code
itself hasn't been updated. However this should ensure that git
correctly preserves history for each file.
This is cleanup relating to a naming decision that we made awhile ago
but never got around to.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=117244827