Application of Peg(400 )In the One-Pot Synthesis of 7-[4-Alkyl- or (Hetero)Aryl-1H-1,2,3-Triazol-1-Yl]Thieno[3,2-B]Pyridines via Snar and Cu(I)-Catalyzed Azide-Alkyne Cycloaddition and Preliminary Evaluation of Their Anti-Tumour Activity