`doctools.py` should also generate outcome group examples

[ahouseholder]

Is your feature request related to a problem? Please describe.

In working on #738, I noticed that the file names in data/json/outcomes are inconsistent with what we have in data/json/decision_points.

Describe the solution you'd like

We should modify src/ssvc/doctools.py so that it automatically generates the outcome group example *.json files when it generates the decision point examples.

[ahouseholder]

Resolved in #795