* Implement RegisterResourceOutputs for Python 3
RegisterResourceOutputs allows Python 3 programs to export stack outputs
and export outputs off of component resources (which, under the hood,
are the same thing).
Adds a new integration test for stack outputs for Python programs, as
well as add a langhost test for register resource outputs.
Fixespulumi/pulumi#2163
* CR: Rename stack_output -> export
Fix integration tests that hardcoded paths to stack_outputs
* Fix one more reference to stack_outputs
