[Indic] Add test for matra group

The spec says: "[{M}+[N]+[H]]", and that's what Uniscribe implements.
We instead do: "{M+[N]+[H]}", which means we allow Nukta and Halant
after all Matras, not just the last one.  It makes more sense.

test/shaping/texts/in-tree/shaper-indic/indic/script-devanagari/misc/MANIFEST

 joiners.txt
 misc.txt
+spec-deviations.txt
 tricky-reordering.txt

test/shaping/texts/in-tree/shaper-indic/indic/script-devanagari/misc/spec-deviations.txt

+सा़े