Improving robustness of Windows build pipeline

[GustavoSilvera]

Finding the most common points of failure in a default Windows build pipeline (zlib, xerces, osm2odr, PythonAPI) and patching them.

1. Added archive link for zlib 1.2.1.1 (here) and Xerces 3.2.3 (here) to follow the compatibilities from 0.9.13
2. Prefer building PythonAPI with python rather than Windows built-in py -3 (better for conda) but fallback if python is not available (here)
3. Create missing directory in PythonAPI if it does not exist, this would otherwise result in a silent error that wouldn't get "fixed" until running make PythonAPI again (here)
4. Add transcoder=windows build flag for xerces (more reliable than the default of ICU) (here)

Also fixed a crash when there was already an EgoVehicle in the map before BeginPlay was called.