Similar to `IntegerRelation::addLocalFloorDiv`, this adds a utility
`IntegerRelation::addLocalModulo` that adds and returns a local variable
that is the modulus of an affine function of the variables modulo some
constant modulus. The function returns the absolute index of the new var
in the relation.
This is computed by first finding the floordiv of `exprs // modulus = q`
and then computing the remainder `result = exprs - q * modulus`.
Signed-off-by: Asra Ali <asraa@google.com>
b045729eb4