feat: podio-vis --upstream-edm and some tests

[wdconinc]

This adds some basic support for extension data models into podio-vis.

Also adds three tests for podio-vis to make sure it doesn't fail. May require graphviz python to be installed in the CI environment.

BEGINRELEASENOTES

• support podio-vis for extension data models

ENDRELEASENOTES

[tmadlener]

Key4hep nightlies should pick up the py-graphviz dependency soon-ish. I would wait until then and run the key4hep workflow once that is in. Unless, you need this very urgently.

[wdconinc]

Not urgently needed; we are also propagating py-graphviz into our environments still (FYI @bspage912).