feat(nix): overhaul nix flake and packages

[gigamonster256]

standardizes dev packages to the regular callPackage style and brings best practices from nixpkgs upstream

maintains compatibility with current nix based CI updates to node_modules hashes

NOTE: this removes the flake-update CI job - read the commit desc for why - open to discussion

Superscedes #8998

would love feedback/get testing from recent nix committers @gbpdt @Alb-O @jerome-benoit