Ortho-Directed Metalation of 3-Carboxy-β-carbolines: Use of the SmI<sub>2</sub>-Cleavable 9-<i>N</i>-(<i>N</i>‘,<i>N</i>‘-Dimethylsulfamoyl) Blocking Group for the Preparation of 9-<i>N</i>-Deprotected 4-Amino Derivatives via Azide Introduction or a Palladium-Catalyzed Cross-Coupling Reaction