make re-usable TypeAdapter instances for client schemas

[zzstoatzz]

moves creation of type adapters out of client method impls

related to #15047

this actually increases import time, which makes sense. there's a question of whether this is really better, since you could argue you only have to construct the type adapter instance if you use that specific client method.

will look into if defer_build can be used here (doesn't seem to apply to config as accepted by TypeAdapter)

[codspeed-hq]

CodSpeed Performance Report

Merging #16089 will not alter performance

_{Comparing make-less-adapters (c2420ee) with main (340e296)}

Summary

✅ 3 untouched benchmarks

[zzstoatzz]

Merging #16089 will degrade performances by 11.69%

this does makes sense, since we're making all of the adapters at import time, but I think this is worth it

[aaazzam]

https://docs.pydantic.dev/latest/concepts/type_adapter/#rebuilding-a-typeadapters-schema