BREAKING: replace custom build scripts with nix

General:
- Switched to yarn to better work with nix-based tooling
- Switched package system to use nix. This stops double dependencies and slow cloud compile times, while providing more compile/runtime support to the Nix project
- Removed container builder in favor of internal container tooling
- Package versions no-longer need to be SemVer compliant
- Removed "piston package spec" files, replaced with nix-flake based runtimes
- Exported nosocket and piston-api as packages within the nix-flake
- Removed repo container
- Switched docker building to nix-based container outputting
- Removed docker compose as this is a single container
- Removed package commands from CLI

Packages:
- Move bash, clojure, cobol, node, python2, python3 to new format
- Remainder of packages still need to be moved

v2 API:
- Removed "version" specifier. To select specific versions, use the v3 api
- Removed "/package" endpoints as this doesn't work with the new nix-based system

v3 API:
- Duplicate of v2 API, except instead of passing in a language name an ID is used intead.

shell.nix

@@ -1,5 +1,11 @@
 { pkgs ? import <nixpkgs> {} }:
   pkgs.mkShell {
     # nativeBuildInputs is usually what you want -- tools you need to run
-    nativeBuildInputs = with pkgs; [ nodejs-15_x jq mkdocs ];
+    nativeBuildInputs = with pkgs; [
+      nodejs-16_x
+      jq
+      mkdocs
+      yarn2nix
+      yarn
+    ];
 }