Build GITR and run Python tests in CI

[stonecoldhughes]

There is currently no automatically verified branch of GITR for everyone to rely on as a base for new development and consistent research results. A CI with github actions needs to be setup to verify this.

container is entirely outside the CMake build system and GITR.
maybe we can do that with CI outside of Docker

best case scenario - in the CI we can run GITR in the container as well as just directly in the CI host.

1. Branch off verified main version - DONE
2. Make main build in a container environment - DONE
3. Make main successfully run Python tests in its environment (locally)
4. Use github actions and .github CI config files to repeat step 3 on github's CI cloud machine

[tyounkin]

TODOs:

• Tim: make sure python tests are passing (locally). Pull "consolidate" branch, build, ctest python. Try inside and outside container.
• Tim: Apply for CADES birthright and look into project cost for group
• Harry: set up mirror?
• Harry: github actions for small tests?
• Run larger tests manually on cloud?

How to know we're done: When we can push to main and have a ctest, python test automatically run on CADES with GPUs. Includes manual build and dockerhub image.