Fix 2gb report xml limit on Windows

[g-maxime]

Windows std::stringstream maximum size is INT_MAX

https://github.com/microsoft/STL/blob/main/stl/inc/sstream#L323

Fixes #841

[JeromeMartinez]

Windows std::stringstream maximum size is INT_MAX

I have doubts that it is what the spec expects!
In any case, it is not bad to avoid std::stringstream when not a lot needed because it uses to be slow.
At long term, replacing other std::stringstream by fmtlib (and later the C++20 std::format version) could be nice, but not urgent.