Proposal: Migrate from CircleCI to Github Actions

[hdost]

The change seems relatively simple and there's no real benefit for this repo as it's a simple Linux java build anyhow.

Reference for How: https://docs.github.com/en/actions/migrating-to-github-actions/migrating-from-circleci-to-github-actions

[fstab]

Hi @hdost, my understanding is that all projects in the Prometheus organization are built with CircleCI (client_golang, client_python, client_ruby, prometheus, alertmanager, pushgateway), and they use a common Prometheus ORB for cross-project tasks like releasing Docker images (not needed by client_java though, as we release via Maven central). Some Projects have Github actions as well, but as far as I can see it's not for releasing, but just for tasks like running a Go linter.

Having the same built tool makes it easy for Prometheus community members to understand the build process for other Prometheus projects. There should be a good reason to switch to a different build tool client_java while all the others use CircleCI. I'm not really missing anything with CircleCI. Do you have anything specific in mind?

[hdost]

That's logical. Will close.