Fix windows build

[oruebel]

• Wrapped std::min calls in parentheses in src/remfile_vfd.cpp. This prevents the Windows min macro from incorrectly expanding the standard library function, which was causing the error C2589: '(': illegal token on right side of '::' error.
• Fixed warning C4365: 'argument': conversion from 'size_t' to 'const __int64', signed/unsigned mismatch [D:\a\aqnwb\aqnwb\build\_deps\remfile-build\remfile.vcxproj] std::vector<uint8_t>(data.begin() + piece_start, data.begin() + piece_end);
• Added Windows to the CI build to make sure this is tested here directly
• Updated test_remfile.c to support Windows

[bendichter]

Thanks @oruebel, this looks good. The library-side changes are minimal and safe: the parenthesized (std::min) calls are the standard workaround for the Windows min macro, and the switch from iterator-based to pointer-based vector construction in load_chunk is semantically identical to what was there before. Everything else is test and CI infrastructure, and the full matrix (including the two new Windows jobs) is green, so I am comfortable merging this as is.

A few minor notes, none of them blocking:

• The comment at the top of tests/http_test_server.hpp still says "POSIX sockets only (Linux/macOS)", which this PR makes untrue. Worth updating in a follow-up.
• The typedef int socklen_t; in the _WIN32 branch duplicates the typedef in ws2tcpip.h. It is legal since the types are identical, but it can probably be dropped.
• An alternative to parenthesizing each std::min call would be defining NOMINMAX on the target for Windows builds, which would also protect any future std::min/std::max uses. The current approach is fine too; I mention it mainly in case we hit this again elsewhere.