Container Image Build Fix - Allow for Push to a different container registry while building from GitHub

[alexlianides]

Add new feature to build_app and build_containerImages called --build-from-github.

This feature, when called, will always build the payload-app image from the ghcr.io container registry entry stored within the user's generated spacefx-config.json. This ensures that the application you are building is calling the Microsoft maintained spacefx-base container image, which serves as the base-layer docker image for all space sdk container images.

This allows users to build new container images with build_app from the Github images, and still push the container image to their desired registry they have push_enabled: true within the containerRegistries stored within spacefx-config.json.