Unsplit vendor import of tzcode 2010n

Historically, to work around CVS limitations, imports on the tzcode
vendor branch were split into subdirectories, which were then merged to
their respective counterparts in contrib. In the Git era, this split is
unnecessary and adds more work.

Undo the split for the most recent vendor import of tzcode 2010n to
prepare for the vendor import of tzcode 2022c.