Move CI to GitHub Actions

[malfet]

This PR migrates CircleCI workflow to GHA and makes a few minor changes:

• Upload intermediary docker containers from GCR to ECR (as they are faster to download and do not incur egress costs to the infra)
• For the same reason, workflows no longer require AWS credentials, as runners provision to have write access to the bucket/ECR
• Skip the logic of rebasing PRs against latest trunk, as GH is doing it automatically
• Build/publish docs on trunk in parallel to CPU tests build
• Rely on GitHub reusable workflows and split workflow into _build.yml, _test.yml and _docs.yml

Test plan:

• Enable codecov collection on PRs and test that it works (see this log)
• Test docs build (see this log)

TODO:

• Test/migrate doc-push step
• Test/migrate code coverage collection step
• Delete config.yml and no-longer used steps from .circleci/common.sh

[JackCaoG]

@malfet Test is green now, is this one ready to be reviewed?

[malfet]

@JackCaoG it's missing codecov and doc push steps, working on adding them now, and than it'll be ready

[malfet]

@JackCaoG I think it is ready now with a small caveat of adding a doc push step, which if you don't mind I'll do after current CI run finishes (want to make sure that codecov upload logic works as expected)

[JackCaoG]

Thanks @malfet this is super exciting. I will take a look tmr after test is green.

[malfet]

Hmm, interestingly job OOMs, (even though linux.4xlarge should have 32Gb of RAM), will try to upgrade to linux.12xlarge, which has 96Gb of RAM

[JackCaoG]

Thanks!

[Subbarker]

was perusing this file for an example to work off of and noticed this typo: metadtaa.json

[malfet]

@Subbarker thanks, fixing in #5172