casbin-cpp: [doc] Benchmark data about casbin-cpp in `casbin.org` maybe wrong.

casbin-cpp benchmark data in official website maybe wrong, RBAC time comlexity maybe O(n) rather than O(1), n is policy numbers in memory. So with data increase in RBAC small, RBAC medium and RBAC large, consumed time will increase. We can ref to this action, and other languge benchmark.
And when I run Large benchmark in my local machine, I can’t get the benchmark result, even I have run it at least one hour. I only get the some small data case benchmark result.

About this issue

This is not common sense because we know C++ will usually be at least 10x faster than Go or Java.

Even I expected it to be a lot faster. We need to look into what is causing the bottleneck. (as far as I can recall, it was related to duktape)

For now we can just provide a manual profiling way to make sure the performance downgrade troubleshooting is not blocked.

Alright, making a new issue for profiling.