driver_remove should return error when file doesn't exist

[sgouache]

Khiops tries to remove several files "just in case" without checking for their existence. In current implementation of driver_remove, we skip the error if the failure is due to a non-existent object. We should instead log the error, return the failed status and set the last error message accordingly. Note: we will probably mute the driver logs by default (setting the loglevel to "quiet"), leaving the responsibility to khiops to log the messages that it finds relevant. All driver logs will still be available by setting GCS_DRIVER_LOGLEVEL to something else than "quiet".

[lucaurelien]

à qualifier dans Khiops-core