server: Support creating files with direct and synchronous I/O
This allows various disk benchmarking software like CrystalDiskMark and ATTO disk benchmark to actually benchmark the disk rather than the file cache
Implementation based on public Microsoft NtCreateFile() documentation: https://learn.microsoft.com/en-us/windows/win32/api/winternl/nf-winternl-ntcreatefile
According to the documentation, Windows forbids FILE_APPEND_DATA and FILE_NO_INTERMEDIATE_BUFFERING being set together, but Linux has no such limitation with the equivalent O_APPEND and O_DIRECT...