nitg-s: retrieve recursively all partial generic types

nitg-s: retrieve recursively all partial generic types

for new G[H[nullable T], Object] and T: X
nitg-s will now find :
	G[H[nullable X], Object]
	H[nullable X]
	nullable X
	Object
as type to generate.

H[nullable X] and nullable X are considered as partial type because they are only used as part of a generic livetype.

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>