[fs][fidl] Replaced filesystem ioctls with FIDL.

This patch allows "ioctl" to be removed from the
C++ VFS Vnode interface.

IOCTL_VFS_MOUNT_FS -> Mount()
IOCTL_VFS_UNMOUNT_FS -> Unmount()
IOCTL_VFS_UNMOUNT_NODE -> UnmounteNode()
IOCTL_VFS_QUERY_FS -> QueryFilesystem()
IOCTL_VFS_MOUNT_MKDIR_FS -> MountAndCreate()
IOCTL_VFS_GET_DEVICE_PATH -> GetDevicePath()
IOCTL_VFS_WATCH_DIR -> WatchDir()

Test: fs-management / fs / blobfs / fvm tests, df manually

Change-Id: Iefe8ec251ca6b8f4e4578ceb61bae6dff7a59e3d