Synthesis, Thermolysis, and Photolysis of the Azoalkanes Spiro[4,5‐diazatricyclo[4.3.0.03,7]non‐4‐ene‐8,2′‐[1.3]dioxolane] and 4,5‐Diazatricyclo[4.3.0.03,7]non‐4‐en‐8‐one: On the Mechanism of the Oxadi‐π‐methane Rearrangement of 5‐Norbornen‐2‐one