[3.14] gh-138432: Improved invalid path checking in zoneinfo.reset_tzpath() (GH-138433) (GH-138777)

* Improve error messages for path-like relative paths and path-like bytes paths.
* TZPATH is now always a tuple of strings.
(cherry picked from commit 859aecc33b82f45e5b7ae30138d28f2a2f33a575)

Co-authored-by: Stephen Morton <git@tungol.org>