Add timezone.

[cdmurph32]

This code only fetches the name of the timezone. The determination of utc offset is left to the runtime.

Issue:
bytecodealliance/wasmtime#4274

WASI Clocks proposal:
WebAssembly/wasi-clocks#48

Relate wasmtime PR:
bytecodealliance/wasmtime#6899

[sunfishcode]

I apologize for the slow response here!

The cap-std crate is intended to focus on features which are provided by Rust's std. What would you think about moving this code to the cap-time-ext crate, which also lives in this repository? We could also move the implementation from cap-primitives into cap-time-ext, so that users that don't need it wouldn't need the iana-time-zone dependency.

[cdmurph32]

No apology necessary. I just figured out how to get it working end-to-end with wasmtime this morning. I didn't even know about the component adapter.

[sunfishcode]

Thanks!