[FEA] Support generation of test graphs as a library feature (C++)

[ChuckHastings]

Networkx supports a whole host of graph generation capabilities as part of the library that users can call when using networkx.

cuGraph has some graph generation capabilities within the testing component. These graph generation capabilities are going to be extended as we migrate things to use the pattern accelerators.

This issue is to migrate the existing graph generation capabilities into libcugraph.so and expose them in the C++ API.

[github-actions]

This issue has been labeled inactive-30d due to no recent activity in the past 30 days. Please close this issue if no further response or action is needed. Otherwise, please respond with a comment indicating any updates or changes to the original issue and/or confirm this issue still needs to be addressed. This issue will be labeled inactive-90d if there is no activity in the next 60 days.