Add pylint action with Google style configuration.

[lucasb-eyer]

This would run pylint with the official Google style configuration on every PR automatically, saving us quite a bit of time.

We can already see results of it in this PR

However, it seems that maybe we should submit the configuration here and fine-tune it a bit? I'm seeing several lint errors that we don't actually hit internally, for example: So we should see if we like this difference, and/or where it comes from, before merging.