A Simple and Efficient Regioselective and Chemoselective Synthesis of New Substituted 3-Methyl-6-arylpyridazine-4-carboxamides and 5-Oxo-3-aryl-5,6-dihydropyrido[4,3-c]pyridazine-8-carbaldehydes: Novel Synthesis of New Substituted Pyridazine Heterocycles