[Lint] Refactor check-doc.py to have a list of folders

Summary:
This will allow us to prevent false positives in the future as /chronik is not scanned for sources nor tests currently.

Currently, behavior is unchanged, /chronik will be added in a future diff.

Test Plan: arc lint, behavior is unchanged

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12678