Add examples for in-code data contexts

[spbail]

We still have a TODO in the example DAG for in-code contexts. I actually implemented them in another repo when testing out Astronomer - we should migrate the 3 examples at the bottom over to this example DAG, test them to make sure they run too, package, and release. That's lines 131 and below in this example: https://github.com/superconductive/astro-ge/blob/main/dags/example_great_expectations_dag.py