suggestion: `@std/kv`

[iuioiua]

I suggest moving @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() until it's implemented in the runtime.

Related #6123

[timreichen]

Is kv stable yet? If not I think we should wait until it is.

[iuioiua]

Whether it's stable or not (which it's not), @std/kv would have to be an unstable package anyway, as it's new.