[SPARK-7391] DAG visualization: auto expand if linked from another viz

This is an addition to #5729.

If you click into a stage from the DAG viz on the job page, you might expect to expand on the stage. However, once you get to the stage page, you actually have to expand the DAG viz there yourself.

This patch makes this happen automatically. It's a small UX improvement.

Author: Andrew Or <andrew@databricks.com>

Closes #5958 from andrewor14/viz-auto-expand and squashes the following commits:

03cd157 [Andrew Or] Automatically expand DAG viz if from job page