chore: add benchmark case for horizontal coedges

[cwangbh]

Hi Angus,

Hope it's been going well for you lately.
Recently in my use case, i found one specific case that is very time consuming, it has many horizontal coedges and looks like the following image:

I have extended the coedge numbers and wrote a simple benchmark file in the pull request. The runtime is approximately to be O(N^2) as I increase the horizontal coedge numbers.

Through profiling, i found most time is spent on the following two functions:
Clipper2Lib::GetMaximaPair
Clipper2Lib::IsValidAelOrder

It seems that this is related to the internal data structure linked list and the search time is O(N). Do you have any suggestions on how to improve this runtime?

[AngusJohnson]

Thanks. I certainly appreciate the feedback. I'm currently occupied with other things, but hope to look at this in the next day or two. Nevertheless I'd be surprised if I can make GetMaximaPair() or IsValidAelOrder() significantly faster, but of course I'd welcome suggestions there too.

[Misa-sudo-coder]

What the heck is going on here?