CREST-9240: update summit-env to produce a top-level manifest

The manifest will be used to determine the source image and tag for the QA data container when running API tests for summit-denali. Subsequent work could use it when creating the task definition for the stack in summit-cloud.

This MR also replaces the node-based yaml-updater image with yq. A new stage is added to the CI pipeline that creates a custom image based on the yq image, adding the other dependencies needed by update-stack.sh. The image is created only when there are changes to the Dockerfile or CI configuration. The image is pushed to the docker registry after it is built. The subsequent build stage uses the custom image.