fix: BlockDevice trait is not imported in fat32-fuse/src/main.rs; delete cargo.lock and update .gitignore

fix: change RuntimeFlags::ZOMBIE(usize) to RuntimeFlags::ZOMBIE(isize), because exit code should be signed number

refactor: merge stop_current_and_run_next, exit_..._next and block_..._next into one function: schedule

fix: disable some test functions, add new test function for SYSCALL_OPEN in user/lib/src/bin/test_fs