Add Sydney timezone

[OrestZborowski-SIG]

It would be useful to support the Sydney timezone.

[jack-pappas]

If you add this, please use the proper tz database name for the timezone: Australia/Sydney for easier compatibility with other libraries/tools.

Ideally, riptable should get rid of the hard-coded timezone information it's maintaining. Instead, it should take a reference on the tzdata package via conda or pip; that package is already a requirement for many other Python libraries, so most users should already have it available in their Python environments. The timezone offset data for all timezones in the tz database can be supported by parsing the timezone offset information from tzdata using the logic from the built-in zoneinfo module in CPython: https://github.com/python/cpython/blob/1c7a1c3be08ee911d347fffd2716f3911ba751f9/Lib/zoneinfo/_zoneinfo.py

Some of the supporting logic from zoneinfo, e.g. converting timestamps between UTC and local time could then just be ported over + adapted to array-style programming, e.g. using rt.searchsorted(..., side='right') instead of bisect.bisect_right(...). Some hypothesis-based tests could be implemented to verify the accuracy of the conversions too, by checking the array-based results against an equivalent list of dt.date / dt.datetime run through the corresponding function from datetime or zoneinfo.