scale: Fix css node ordering and expected results

scale: Fix css node ordering and expected results

Add :dir(ltr) where expected, i.e. everywhere we now have a widget but
had a gadget before.
Also, fix the expected output to expect mark subnodes in the order
specified in the GtkScale does, i.e.

├── mark
    ├── [label]
    ╰── indicator

for marks at the top of the scale and

├── mark
    ├── indicator
    ╰── [label]

For marks at the bottom of the scale.