Draft: Improve static menu entry generation for other OSes
This is an untested draft opened for comments and feedback.
Changes:
- Generate a static menu only if other supported OSes are detected and os-prober is disabled or not present.
- Add support for EFI boot loaders.
- Use submenus for extra Linux entries.
Support for macosx and minix is missing, but I am feeling lazy.
Edited by Pascal Hambourg