fix: move sleep to have all code in src

[AuHau]

So... 😅

My IDE was trigger-happy and I haven't noticed it. When implementing the waitForUsable feature, I have copy&pasted Aron's solution, which used the sleep function and IDE noticed that we have this function in test/utils.ts file so it just imported that and I have not noticed that.

Thanks to this the tsc compilation changed the structure of the compiled files as it has to now import something from ./test folder and so it changed the ./dist/cjs/ folder structure into containing subfolders src and test as this:

cjs
├── package.json
├── src
│   ├── bee-debug.js
│   ├── bee.js
│   ├── chunk
│   ├── feed
│   ├── index.js
│   ├── modules
│   ├── types
│   └── utils
└── test
    └── utils.js

This, unfortunately, breaks the package as the entry file ./dist/cjs/index.js is not in the expected place.

[bee-worker]

Release v4.1.1 addresses this.

[agazso]

Maybe we can add a test for this in the release pipeline so we don't accidentally break this in the future?

[AuHau]

@agazso #698