Draft: Scinotes backup files were not always deleted
fixes #17108 partly. Proposal is to improve the autosave/backup feature by deleting backup files when the editor pane is closed (and not until Scilab is exited). This MR does not fix the following issues:
- when a file is saved in a different folder than the current directory, the backup file is always created in the current directory.
- when editing a new file from scratch, there is no backup creation until the current file is saved by the user.
Edited by Stéphane MOTTELET