suggestion: `@std/kv`

I suggest moving [`@deno/kv-utils`](https://jsr.io/@deno/kv-utils) to `@std/kv`. While these utilities have fairly niche use cases, creating `@std/kv` can offer some possible benefits:
1. These utilities would have far greater visibility in the Deno Standard Library. I only just discovered `@deno/kv-utils` and it's been around for a few months.
2. Can increase awareness of Deno KV.
3. Increases the chances that devs imagine up and create better tools for Deno KV.
4. Possibly serve as a test bench for ideas that could be implemented in the runtime. E.g. a JavaScript/TypeScript version of [`Deno.Kv.count()`](https://github.com/denoland/deno/issues/18965) until it's implemented in the runtime.

Related #6123