alternate method to find mapstartindex using terrains

[mrosack]

There was one game on PYDT that was failing because the searchBuffer just wasn't in the file (https://github.com/pydt/api/blob/master/_docker/civ6_pipeline/node_handler/_testdata/files/2a28549b-2ab4-4959-8403-fd9a94b637d0.Civ6Save). This fallback method will find the first terrain in the file and use that to figure out the mapstartindex.

[rcannood]

Hey Mike!

@Grifs and I did quite a lot of digging around in figuring out the structure of the search buffers (when they occur and why) and the mapsearchindex (by figuring out the structure that comes before the tile information).

Unfortunately I'm on holidays until early mid August. I'm happy to look into this pr and merge it for the time being, but I'm inclined to refactor this pipeline such that it works with the work that was done at GitHub.com/rcannood/civ6save_analysis.

Would that be okay with you?

Out of curiosity, would it be possible to provide a random subsample of save files from pydt, just so i can check whether our imHex pattern works
across the board?

[mrosack]

yeah, sure, this can wait if you have a better solution - you can see my PYDT test files/cases at https://github.com/pydt/api/tree/master/_docker/civ6_pipeline/node_handler/_testdata