Building inside the container allows Windows and MacOS users to also build this binary. Thanks to a new feature from docker, `--mount=type=cache`, rebuilding layers is fast without any additional hacks.
This patch adds a workflow that automatically publishes a docker image of our `ping` interop-test binaries on every release. Releases are different from Git tags. We publish a tag for each version of each crate but only a single release for each version of the `libp2p` crate.
Alternatively, this workflow can also be triggered manually:
1. Select the Git ref you want to run the workflow on. This should be the version of `libp2p` you want to publish the test binary for. For example, if you want to publish a version of the test binary for a hotfix release of a sub-crate, you would pick the respective tag of the hotfix release.
2. Choose the tag of the docker image.
To resolve https://github.com/libp2p/test-plans/issues/112, I am planning to create branches off current master that hardcodes the libp2p version in the test-binary to a particular one and then trigger this workflow for the respective branch.
We make the binary that should be copied into the container configurable via a build time `ARG`. This will allow us to reuse the same `Dockerfile` once we write more tests.
Additionally, this allows us to remove some of the directory switching and creation code. In order to not send the entire repository over to the docker daemon as a build context, we introduce a `.dockerignore` file that only allows select binary to be sent over.
The downside of this is that we need to extend this ignore file every time we add a new test. This shouldn't happen very often though and is easily discovered because the building of the docker container will fail.
