PERF: Hand Written Parser for Timedelta ISO 8601 Construction
See comment in #19039 - a hand written parser to replace the [regular expression](https://github.com/WillAyd/pandas/blob/6bab9dab85314918d01019f59944e7f278222a28/pandas/_libs/tslibs/timedeltas.pyx#L510) in ``timedeltas.pyx`` may provide performance benefits when constructing a ``Timedelta`` from an ``ISO 8601 Duration`` string