changes FileHandle type on Windows (#24910)

On windows, `HANDLE` type values are converted to `syncio.FileHandle` in
`lib/std/syncio.nim`, `lib/pure/memfiles.nim` and `lib/pure/osproc.nim`.
`HANDLE` type is `void *` on Windows and its size is larger then `cint`.

https://learn.microsoft.com/en-us/windows/win32/winprog/windows-data-types

This PR change `syncio.FileHandle` type so that converting `HANDLE` type
to `syncio.FileHandle` doesn't lose bits.

We can keep `FileHandle` unchanged and change some of parameter/return
type from `FileHandle` to an type same size to `HANDLE`, but it is
breaking change.

lib/windows/winlean.nim

@@ -815,7 +815,7 @@ proc WSASendTo*(s: SocketHandle, buf: ptr TWSABuf, bufCount: DWORD,
                 completionProc: POVERLAPPED_COMPLETION_ROUTINE): cint {.
      stdcall, importc: "WSASendTo", dynlib: "Ws2_32.dll".}
 
-proc get_osfhandle*(fd:FileHandle): Handle {.
+proc get_osfhandle*(fd: cint): Handle {.
   importc: "_get_osfhandle", header:"<io.h>".}
 
 proc getSystemTimes*(lpIdleTime, lpKernelTime,