Add Github Action to run TPU tests. (#2376)

* Add Github Action to run TPU tests.

* Trigger new Github Actions run.

* Clean up more comments.

* Use different fixed version of ml-testing-accelerators and update config to match.

* use cluster in us-central1-a

* Run 'gcloud logging read' directly without 'echo' to preserve newlines.

* cat coverage.xml on the TPU VM side and upload xml on the Github Action side

* Use new commit on ml-testing-accelerators so command runs fully.

* Preserve newlines in the xml and use if: always() temporarily to upload codecov

* Use pytorch_lightning for coverage instead of pytorch-lightning

* Remove the debug cat of coverage xml

* Apply suggestions from code review

* jsonnet rename

* name

* add codecov flags

* add codecov flags

* codecov

* codecov

* revert codecov

* Clean up after apt-get and remove old TODOs.

* More codefactor cleanups.

* drone

* drone

* disable codecov

* cleaning

* docker py versions

* docker py 3.7

* readme

* bash

* docker

* freeze conda

* py3.6

* Stop using apt-get clean.

* Dont rm pytorch-lightning

* Update docker/tpu/Dockerfile

* Longer timeout in the Github Action to wait for GKE to finish.

* job1

* job2

* job3

Co-authored-by: Jirka Borovec <[email protected]>
Co-authored-by: Jirka <[email protected]>