Add `extract_paths` python API for working with individual paths from consolidated path return values

[rlratzel]

The C API has the cugraph_extract_paths API, and this needs to be added to the Python API in order to allow users to work with individual paths from the consolidated path return values of various traversal APIs.

• [ ] Add examples using extract_paths() with multi_source_bfs()
• [ ] Add tests to python suites (pylibcugraph, cugraph) covering extracting paths from multi_source_bfs()
• [ ] Add extract_paths() API to pylibcugraph
• [ ] Add extract_paths() API to cugraph
• [ ] Update relevant docs

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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.

[github-actions[bot]]

This issue has been labeled inactive-90d due to no recent activity in the past 90 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.

[github-actions[bot]]

This issue has been labeled inactive-90d due to no recent activity in the past 90 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.