Add feature tests for all algorithms

[acarbonetto]

Is your feature request related to a problem? Please describe.

Add backend testing suite for nx-neptune. See: networkx/networkx#8258 (review)

Describe the solution you'd like
Testing suite that can be run to ensure networkx with nx-neptune backend algorithms do not break.

Describe alternatives you've considered
N/A

Additional context
N/A