feat(devcontainer): absorb common-utils feature into Containerfile

This will hopefully cut down on build-time and was an interesting exercise

Signed-off-by: Vegard Hagen <[email protected]>

.github/.devcontainer/devcontainer.json

@@ -3,15 +3,6 @@
   "build": {
     "dockerfile": "Containerfile"
   },
-  "features": {
-    "ghcr.io/devcontainers/features/common-utils:2": {
-      "installZsh": true,
-      "configureZshAsDefaultShell": true,
-      "installOhMyZsh": true,
-      "installOhMyZshConfig": true,
-      "upgradePackages": true,
-      "username": "dev"
-    },
-  },
+  "features": {},
   "remoteUser": "dev"
 }