mount-util: use modern mount_setattr() syscall for bind_remount_one_with_mountinfo()

New kernels have a nice syscall for changing bind mount flags. Let's use
it. This makes the complex libmount based iteration logic unnecessary.

src/basic/missing_syscall.h

@@ -465,10 +465,18 @@ struct mount_attr;
 #define MOUNT_ATTR_IDMAP 0x00100000
 #endif
 
+#ifndef MOUNT_ATTR_NOSYMFOLLOW
+#define MOUNT_ATTR_NOSYMFOLLOW 0x00200000
+#endif
+
 #ifndef AT_RECURSIVE
 #define AT_RECURSIVE 0x8000
 #endif
 
+#ifndef MOUNT_ATTR_SIZE_VER0
+#define MOUNT_ATTR_SIZE_VER0 32
+#endif
+
 static inline int missing_mount_setattr(
                 int dfd,
                 const char *path,