refactor common utils
Description
bring and improve refactoring of CommonUtils class from forgiven MR for !237 (closed)
Technical details
Try to keep it atomic
- Fix All warning in Commonutils class
- Remove code specific to file manipulation into a dedicated FileUtils class (in Kotlin) and thus update all import and usage call to CommonUtils for those method
Note: No modification of existing behaviour, just code cleaning
Issues
https://gitlab.e.foundation/e/os/backlog/-/issues/1246