Add test for pipelines in examples directory
Summary: This diff a small test to the examples tests that simply executes dagster pipeline list for the examples directory. This will help catch any issues with pipelines in our examples.
Test Plan: Introduce broken pipeline, run test, check that it fails
Reviewers: #ft, alangenfeld
Reviewed By: #ft, alangenfeld
Differential Revision: https://dagster.phacility.com/D1375