[KV Feedback]: Change default write/read region for free tier

### 🔍

- [X] Did you search for existing issues?

### Type of feedback

Feature request

### Description

Hi,

I was wondering whether it would be possible to enable free tier users to configure the default write/read Deno KV regions.

I am in Europe, so playing around with a deployed instance feels quite sluggish, it would be great if I could try it out from a region that is closer to me.

### Steps to reproduce (if applicable)

_No response_

### Expected behavior (if applicable)

_No response_

### Possible solution (if applicable)

_No response_

### Additional context

_No response_