in order to improve containers

• create docker image from Dockerfile
• create docker image from nix flake

in order to improve runtime

• use custom runner on one of our servers

in order to improve platform coverage

• run tests with cuda backend
• add tests for macos

in order to improve bug hunting

• at the end of a test run, we could save the docker container state into a new image. that image can then be investigated by running it again