Expand KV SDK to target all of WASI KV

The KV SDK only supports [`store`](https://spinframework.github.io/spin-python-sdk/wit/imports/key_value.html#spin_sdk.wit.imports.key_value.Store) operations with WASI KV. This is an issue to track adding the batch and atomic operations of the [WASI KV world](https://github.com/WebAssembly/wasi-keyvalue/blob/main/wit/world.wit) to the SDK.