Remove the nesting of classes in RelationCounterField.
Review Request #9755 — Created March 7, 2018 and submitted
This is the first in a series of changes to simplify the complexity in
RelationCounterField, disentangling the responsibilities between
classes and reducing chances of deadlocks or other issues.
In this change, the nested classes (
RelationTracker) have been moved out from
the top level of the new module for the field. This just helps keep
things a bit more organized for the next few steps and reduces the
amount of churn that has to be reviewed.
Unit tests pass.