pokec medium: exact N hop reachability

[adsharma]

Results from 0.19.0:

code: https://github.com/adsharma/falkordb-benchmark/tree/ladybug
data: https://huggingface.co/datasets/ladybugdb/pokec-medium/tree/main
output: https://gist.github.com/adsharma/bfb9b8828b55371a03a61feb2e42a936

Optimization opportunities:

• Avoid hash joins for count queries
• Look into better memory layout for faster traversal

[adsharma]

Similar optimization: #646