Expand KV SDK to target all of WASI KV

The KV SDK only supports [store operations](https://spinframework.github.io/spin-js-sdk/v2.3/interfaces/Kv.Store.html) 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.