Rebase to 2022agtz from https://github.com/JodaOrg/global-tz

Rebase to 2022agtz from https://github.com/JodaOrg/global-tz
This version is derived from the IANA 2022a tzdata but with some
pre-1970 data restored that had been moved to the backzone file
(which we do not currently ship).
From this point on, we will follow the global-tz fork.