Add checkpointer tests to CircleCI

[mcgibbon]

Purpose

This PR adds checkpointer tests to CircleCI, as a top-level "savepoint" test.

Code changes:

• Added checkpointer calls to Remapping and TracerAdvection classes

Infrastructure changes:

• increase resource class for driver_savepoints_mpi and test_mpi_54rank to xlarge
• add test_savepoint CircleCI plan which runs top-level savepoint tests, currently only checkpointer tests
• add test_savepoint top-level makefile target (in contrast to savepoint_tests target, which is really the dycore tests only)

Checklist

Before submitting this PR, please make sure:

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