Move calculated_point_estimates logic into `CatEstimator` base class

[drewoldag]

I started implementing logic to obey self.config.calculated_point_estimates in the various subclasses of CatEstimator assuming that the work to actually calculate the point estimates would be slightly different for each estimator. In fact it is largely the same, so the logic can be moved into CatEstimator base class.

[drewoldag]

Going to do a little more work on this issue:

• [ ] Abstract the point estimate code into a mixin class.
• [ ] Make a call to PointEstimateMixin.calculate_point_estimate in the _do_chunk_output.