ALMACAL – VI. Molecular gas mass density across cosmic time via a blind search for intervening molecular absorbers by Klitsch, A, Peroux, C, Zwaan, MA, Smail, I, Nelson, D, Popping, G, Chen, CC, Diemer, B, Ivison, RJ, Allison, JR, Muller, S, Swinbank, AM, Hamanowicz, A, Biggs, AD, Dutta, R