* nix: flake: fix improperly using prev.callPackage
* flake: cleanup with let blocks
* flake: make overlays use recursive packages
flake: separate overlays into multiple, combine into default
* nix: overlays: extract to own file
* flake: devShells: remove stdenv override
* overlays: hl-pkgs: xdph: remove needless overlay
Since the packages are now built with the overlays combined from inputs
and self, overriding specific dependencies (anywhere) is no longer
necessary.
* nix: overlays: extras: include xdph and share-picker
* nix: overlays: hl-pkgs: remove stdenv override
