Restore Nix devShell support (#2890)

* nix: Avoid Linux only packages on macOS

* nix: Update flake inputs to get new compiler

In particular, updating nixpkgs & rust-overlay gets us Rust 1.80.1

* Fix partialeq for coroutine

* add a comment about manual implementation of traits for coroutine

---------

Co-authored-by: Evan Almloff <evanalmloff@gmail.com>

flake.nix

@@ -26,6 +26,7 @@
             pkgs.openssl
             pkgs.libiconv
             pkgs.pkg-config
+          ] ++ lib.optionals pkgs.stdenv.isLinux [
             pkgs.glib
             pkgs.gtk3
             pkgs.libsoup_3