MoveMapGenerator: add proper multithreading support

[schell244]

🍰 Pullrequest

Allow mmap extraction to run properly multi threaded.
No changes have been made to the extraction logic itself, some funtions where just moved into TileWorker to run asynchronous.
Depending on the cpu, mmaps can now be build in <1 hour.

How2Test

• start mmap extraction as usual
• select number of threads to be used
• resulting mmaps are the same as without those changes

Todo / Checklist

• None

[mserajnik]

I guess when it’s run from mmap_extract.py it shouldn’t prompt the user but instead just select 1 thread automatically (since mmap_extract.py already spawns multiple workers).

[schell244]

@mserajnik can you maybe give it try and confirm that mmap_extract.py now works as expected?

[mserajnik]

@schell244 Currently not at home, but I’ll give it a try later today or tomorrow at the latest!

[mserajnik]

I'm building Docker images off of this PR right now and will test it tomorrow morning.

In the meantime, because it came to my mind: one could make the argument to remove the mmap_extract.py script altogether if MoveMapGenerator now supports multi-threading itself. However, I would keep it for two reasons:

1. I think the output of mmap_extract.py (that I implemented via Use concurrent.futures and improve user feedback in mmap_extract.py. #2559) is a better overview for the average end user than the elaborate MoveMapGenerator output
2. Removing the script now would potentially break VMaNGOS-related projects that rely on it (e.g., I use it for my Docker setup; of course, I monitor VMaNGOS development closely and could easily adjust it, but not everyone might do that)