Move travis CI to github actions

**Is your feature request related to a problem? Please describe.**
The travis CI jobs we run now take over an hour to complete, they used to take 15 minutes.

**Describe the solution you'd like**
Move away from travis and use a CI provider that doesn't throttle our usage so heavily.

The issue names the current Travis CI jobs and GitHub Actions as the target, but specifies no files or tests. Start by locating the repository's Travis configuration and CI entry points, then compare job coverage and runtime. Done means equivalent CI runs on GitHub Actions without Travis throttling.

Written by the indexing model from the issue text.