Move to prebuilt (#170969)

.devcontainer/prebuilt/prepare.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+# This file contains the steps that should be run when building a "cache" image with contents that should be
+# layered directly **on top of the source tree** once a dev container is created. This avoids having to run long
+# running commands like "yarn install" from the ground up. Developers (and should) still run these commands
+# after the actual dev container is created, but only differences will be processed.
+
+yarn install
+yarn electron