feature: add __str__ methods to queryLineage output classes

[ytlee93]

Issue #, if available:

Description of changes: add str methods to queryLineage output classes Edge, Vertex', and LineageQueryResult` for a string representation of an instance, it will be evoked when calling print() on the object to have a more informative output

Testing done:

Merge Checklist

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[Snoyark]

Can you merge the 3 commits into one to describe the overall change?

[Snoyark]

What does this look like?