RFC DagsterType.name -> DagsterType.unique_name
There are a bunch of bad error messages since name on DagsterType is this sort of confusing property related to uniqueness, and display_name is the thing you want.
To address this, self.name -> self._name and add a getter for unique_name, and update all the callsites to use either display or unique name accordingly.
This diff doesn't change the input arg to DagsterType, since i think that isn't as problematic and is more costly to change.
Test Plan: bk
Reviewers: schrockn, dgibson, max, rexledesma
Reviewed By: dgibson
Differential Revision: https://dagster.phacility.com/D5111