Migrate from CircleCI to Github Actions

[cthain]

Changes proposed in this PR:

• Remove CircleCI config
• Add Github actions config
• Add codeowners file
• Add dependabot for GHA
• Fix some acceptance tests with race conditions
• Remove custom docker test image because it's no longer required.

How I've tested this PR:

• Acceptance tests running in GHA

How I expect reviewers to test this PR:

:eyes:

Checklist:

• [x] Tests updated
• [x] ~CHANGELOG entry added~ Not applicable

[cthain]

Should we re-run copywrite on your new CI files? I'm sure you can manually copy-paste as well.

Good catch :facepalm: .. I forgot about the copywrite headers. I'll add them to the new files manually :+1: