Method read_bytes

Reads bytes into the destination `VmWriter` from the user space of the current process. If the reading is completely successful, returns `Ok`. Otherwise, it returns `Err`. If the destination `VmWriter` (`dest`) is empty, this function still checks if the current task and user space are available. If they are, it returns `Ok`.

(&self, src: Vaddr, dest: &mut VmWriter<'_, Infallible>)