Build CI image

[mitchellhenke]

🛠 Summary of changes

This PR brings over the image build process for the CI image from https://github.com/18F/identity-devops.

[timothy-spencer]

I don't think that you technically need the ecr scanning stuff for CI/review_app images, but it's probably a good thing to have it visible so that you can scan through them and make sure they are fixed (if possible).

Approved! It will be good to have all this under the appdev team's control.

[mitchellhenke]

I don't think that you technically need the ecr scanning stuff for CI/review_app images, but it's probably a good thing to have it visible so that you can scan through them and make sure they are fixed (if possible).

Approved! It will be good to have all this under the appdev team's control.

The ECR scanning for review apps already existed from @stephencshelton in #8781, my changes are turning it into a template to avoid repeating a bunch for scanning the CI image and the review app image