Adjusted the warning message to be more descriptive (#82052)
## Improve warning message for multiple lockfiles detection
### What?
Enhances the warning message when multiple lockfiles are detected to
provide clearer guidance to users.
### Why?
The previous warning message was less informative and didn't provide
clear instructions on how to resolve the issue. The improved message
explicitly mentions:
- That Next.js is inferring the workspace root
- How to silence the warning by setting `turbopack.root` in the Next.js
config
- A link to documentation for more information
### How?
Updated the warning text to be more descriptive and helpful, including a
link to the relevant documentation.
<img width="1433" height="306" alt="image"
src="https://github.com/user-attachments/assets/f92b3dd3-061c-45d0-8135-03b625079256"
/>
Addresses #81864
