Adds node attributes to visualize_execution based on context

[skrawcz]

For inputs -- they will be shown as dotted outlines. For outputs -- they will be shown as rectangles.
Changes UD -> Input to make it clearer what this is too.

This then leaves room for more attribute manipulation.

Adjusts unit tests accordingly.

Changes

• graph.py
• driver.py

How I tested this

• unit tests
• ran visualization example

Notes

• TODO: regenerate all visualization images in docs.

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[skrawcz]

this is what things will look like now -- also change UD to Input.

[elijahbenizzy]

Looks good we should probably regenerate all the examples at some point?

[skrawcz]

Looks good we should probably regenerate all the examples at some point?

yes it's a TODO.