Migrate from Travis to GitHub Actions.

[vitaliyf]

@jeffwidman, this is a first cut at addressing #2356.

I attempted to convert from Travis to GitHub actions as-is. The only exceptions is that old Python 3.x are no longer supported by GitHub, so I dropped them. I also dropped pypy2.7.

There are failures, but I didn't investigate too much into why and whether they are because of GitHut itself. I don't have too much expertise in kafka-python itself, but I'm happy to provide a bit of GitHub Actions help.

You can see results of the current workflow here: https://github.com/vitaliyf/kafka-python/actions/runs/4332483559

If you want to me to continue pursuing this, the questions I have are:

• Should Python 2.7 be dropped?
• Should we add newer Python 3.x all the way to 3.11?
  • Do you also want pypy 3.8 and 3.9?
• Should we drop antique Kafka versions, and if so - how far?
• Should we add latest Kafka versions, all the way to 3.4?
  • Java 8 was deprecated in Kafka 3.0+, should we switch to 11 or 17?
• Do we want to continue using tox or just run pytest/pylint directly?

---

This change is 

[jeffwidman]

Thanks!

However, right now I'm not investing much time actively maintaining this project... that may change down the road, but at least right now it's not something I can spend much time on.

Perhaps you'd be interested in helping out as an active maintainer?
See: #2290.