Treating [K$_4$(H$_2$O)$_{0.5}$][SnTe$_4$] with PPh$_4^+$ or AsPh$_4^+$: Formation of a Highly Air‐Stable Tellurostannate Salt, a Tellurolate with One‐Coordinate Te Atoms, and a Polytelluride Salt with $_∞^1$[Te$_4$(H$_2$O)$_2$]$^{2-}$ Chains