Syntheses and Structures of Solvated Tetrasodiumtetrachalcogenostannates [Na4(en)4][SnE4] (en = 1,2‐diaminoethane; E = Te, Se), and their Reactions Toward Further Ternary or Quaternary Chalcogenometallates [Mn(en)3]2[Sn2Te6]·4H2O or [Na10(H2O)34][Mn4(μ4‐Se)(SnSe4)4]