Feature or enhancement

Migrate_zoneinfo.c to argument clinic.

It is proposed by@vstinner and@pganssle
Link:#19909 (comment)

Pitch

This will improve several things:

1. help() onZoneInfo methods. Here's how it looks now:

>>> help(zoneinfo.ZoneInfo.clear_cache)Help on built-in function clear_cache:clear_cache(...) method of builtins.type instance    Clear the ZoneInfo cache.

2. Add__text_signature__ property to methods, it is very useful: for example,python/typeshed uses it to be sure that stubs and implementation match
3. Move all argument parsing to clinic, which is more convenient

Previous discussion

1. PEP 615: Add zoneinfo module #84683
2. bpo-40503: Add tests and implementation for ZoneInfo #19909
3. bpo-40503: Add tests and implementation for ZoneInfo #19909 (comment)

I will send a PR for this today :)