Replace circleci with github actions

**Is your feature request related to a problem? Please describe.**
Circleci is nice and free -- but it's slow and doesn't have conditional ways to run. i.e. if we only change a certain
part of the repo, all tests still need to run on circleci.

**Describe the solution you'd like**
We move to github actions for all tests.

Each test that circleci runs:
- is translated to a github action
- it is triggered only for the paths it handles

**Describe alternatives you've considered**
Not doing this.

**Additional context**
see .circleci folder for details and what would need to be migrated / scoped.