Photochemical trans‐cis Isomerization of Donor/Acceptor‐Substituted (E)‐Hex‐3‐ene‐1,5‐diynes (1,2‐Diethynylethenes, DEEs) and 3,4‐Diethynylhex‐3‐ene‐1,5‐diynes (Tetraethynylethenes, TEEs)