Add validations for HardhatUserConfig.paths

[zoeyTM]

The paths field was added in parallel with the config validations and slipped through the cracks of being included. We should add some simple validations for them inside v-next/core/src/internal/config-validation.ts (probably in the collectValidationErrorsForUserConfig function)

[Tmthang1601]

Hi @zoeyTM , I cant find any collectValidationErrorsForUserConfig function in config-validation.ts, Can you explain the issue more clearly, I really wanna do it

[Tmthang1601]

Hi, I have added validation checks for the paths field in the collectValidationErrorsForUserConfig function. Specifically:

• Check if paths is an object.

• For each path in paths:

1. Check if it is a string.

2. Check if it is an absolute path.

3. Check if the path exists.

Validation errors will be added to the validationErrors array if any of these checks fail.

I am planning to create a pull request for you to review, and I look forward to your feedback as I am eager to have my PR successfully merged.