Module `Data.Time.Format.Internal` was used by `timezone-series`

Hi,

`time` 1.15 hides the `Data.Time.Format.Internal` module. It just so happens that [timezone-series](https://hackage.haskell.org/package/timezone-series) depends on it in its [Data/Time/LocalTime/TimeZone/Series.hs](https://github.com/ygale/timezone-series/blob/master/Data/Time/LocalTime/TimeZone/Series.hs) module. The corresponding issue is https://github.com/ygale/timezone-series/issues/41.

I've opened this issue per the comment at https://github.com/haskell/time/blob/39f16ac03428ac830d7521727002893afb6780a5/lib/Data/Time/Format/Internal.hs#L5

Start by reading lib/Data/Time/Format/Internal.hs around the referenced module-hiding note, then inspect timezone-series's Data/Time/LocalTime/TimeZone/Series.hs and issue 41. Confirm what breaks with time 1.15 and identify the intended compatibility resolution; done means timezone-series no longer depends on an unavailable internal module and the relevant tests pass.

Written by the indexing model from the issue text.