Add sum_to_zero constraint, free, and check based on ILR transform #4354

Job	Run time
mix/fun tests 1	2h 19m 50s
mix/fun tests 2	1h 34m 20s
fwd tests and non-fun mix tests	58m 22s
prim and rev tests	2h 52m 49s
	7h 45m 21s

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