Feature: pipeline for building metal3 image and using it in integration test

[lentzi90]

There doesn't seem to be a way to run integration tests with a freshly built metal3 image. The closest I could find is the metal3_dev_tools_integration_test.pipeline, which only builds the node images, not the metal3 images. I think it would be awesome if we could expand this so that it can also build the metal3 images when needed.