UI font has regressions

[simoncozens]

It looks like the UI font should have (but no longer has) different feature code to the non-UI font. In particular, deep conjuncts should be replaced with UI/alt forms:

$ shape ~/Downloads/android_fonts-master/api_level/30/NotoSansDevanagariUI-Regular.otf 'कड्र्ट्रुष्ट्र्ठ्रु'
[kadeva=0+762|ddaraprehalfUIdeva=1+577|ttaaltdeva=5+504|vattuudeva=5@-7,0+0|ssaprehalfdeva=9+376|ttaraprehalfUIdeva=9+504|tthaaltdeva=15+585|vattuudeva=15@-46,0+0]

But this is not happening in our UI builds:

$ shape variable_ttf/NotoSansDevanagariUI-VF.ttf 'कड्र्ट्रुष्ट्र्ठ्रु'
[uni0915=0+762|uni0921=1+577|vattuviramalowdeva=1@-38,0+0|uni091F=5+504|vattuulowdeva=5@-5,0+0|ssattadeva=9+584|vattuviramalowdeva=9@-42,0+0|uni0920=15+585|vattuulowdeva=15@-54,0+0]

And some conjuncts with vowel signs should not be formed at all:

$ shape ~/Downloads/android_fonts-master/api_level/30/NotoSansDevanagariUI-Regular.otf 'कद्घृट्ठूड्डू'
[kadeva=0+762|daprehalfdeva=1+520|ghadeva=1+591|rvocalicvowelsigndeva=1+0|ttaprehalfdeva=5+504|tthadeva=5+585|uuvowelsigndeva=5@-93,0+0|ddaprehalfdeva=9+577|ddadeva=9+577|uuvowelsigndeva=9@-77,0+0]

But in current builds, they are being:

$ shape variable_ttf/NotoSansDevanagariUI-VF.ttf 'कड्र्ट्रुष्ट्र्ठ्रु'
[uni0915=0+762|uni0921=1+577|vattuviramalowdeva=1@-38,0+0|uni091F=5+504|vattuulowdeva=5@-5,0+0|ssattadeva=9+584|vattuviramalowdeva=9@-42,0+0|uni0920=15+585|vattuulowdeva=15@-54,0+0]

[simoncozens]

I've fixed these by splitting off the UI source to another file.