{element-desktop,schildichat}-wayland: use writeScriptBin instead of writeScript
{element-desktop,schildichat}-wayland: use writeScriptBin instead of writeScript

This resolves issues with buildEnv (and probably other tools too),
putting the resulting files into $out/bin.  Fixes #157507.

We also change the script names back to the ones without the -wayland
suffix, since the old `useWayland` feature flag didn't add it either,
which may have broken downstream configs.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs