feat: use fs.WalkDir instead of filepath.WalkDir

[lebauce]

Description

In fs walker, filepath.WalkDir is used when fs.WalkDir is used almost everywhere else.
There are subtle differences, for instance the root directory being a symlink, between
the 2 causing inconsistencies between the fs walk and deb post analyze walk.
This PR switches the fs walker to the newer fs.WalkDir interface.

Related issues

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Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
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[DmitriyLewen]

Hello @lebauce
Thanks for your PR!

Looks like the tests are broken now.
Can you take a look?

Regards, Dmitriy

[lebauce]

@DmitriyLewen Yes, sorry about that. Fixing the tests and putting it as "draft" until it's fixed

[github-actions]

This PR is stale because it has been labeled with inactivity.