Extend CircleCI to include sequential tests and cpu backend

[mcgibbon]

Purpose

This PR adds configuration to CircleCI to run sequential fv3core tests and run fv3core translate tests on the cpu backend. This will allow us to remove these configurations from daint.

Infrastructure changes:

• Added fv3core sequential tests to CircleCI
• Added "gt:cpu_ifirst" backend to CircleCI translate tests other than 54-rank test

Checklist

Before submitting this PR, please make sure:

• [x] You have followed the coding standards guidelines established at Code Review Checklist.
• [x] Docstrings and type hints are added to new and updated routines, as appropriate
• [x] All relevant documentation has been updated or added (e.g. README, CONTRIBUTING docs)
• [x] For each public change and fix in pace-util, HISTORY has been updated
• [x] Unit tests are added or updated for non-stencil code changes

Additionally, if this PR contains code authored by new contributors:

• [ ] The names of all the new contributors have been added to CONTRIBUTORS.md

[mcgibbon]

jenkins mostly passed, failures were intermittent issues: https://jenkins.ginko.ch/job/pace_PR/2769/

[mcgibbon]

launch jenkins