Run CI on Perlmutter

Action Items
- [x] Rename https://github.com/buildtesters/buildtest/blob/devel/.gitlab/cori.yml file to something like `nersc.yml` 
- [x] Rename https://github.com/buildtesters/buildtest/blob/devel/tests/test_cori.py to `test_nersc.py` and add method to run on Perlmutter
- [x] Make use of new gitlab runner to run jobs via user [bdtest](https://iris.nersc.gov/user/99914/info)