Force formatting of coordinate sent to OSRM to 6 decimals

[greenscientist]

Right now, when creating the query string for the OSRM queries we use C++ to_string which format the float to 6 decimals, which is exactly the precision that we want.
C++23 seem to change the way that to_string operate, which might change the default decimal length.
We should

1. Add a unit test to valide that we format the query string with the expected precision
2. Use a different formatter to fix the decimals ourselves