fix(vfs): migrate IOCP backend to windows-sys 0.61

windows-sys 0.61 changed HANDLE from isize to *mut c_void, so
NULL_HANDLE is now std::ptr::null_mut() instead of 0. Update the
Cargo.toml version constraint to match.

Author: farhan-syah

Cargo.toml

@@ -46,7 +46,7 @@ features = ["rt", "macros", "sync", "io-util", "time"]
 libc = "0.2"
 
 [target.'cfg(windows)'.dependencies]
-windows-sys = { version = "0.52", features = [
+windows-sys = { version = "0.61", features = [
     "Win32_Foundation",
     "Win32_Storage_FileSystem",
     "Win32_System_IO",

src/vfs/iocp/port.rs

@@ -19,9 +19,9 @@ use windows_sys::Win32::System::IO::{
     CreateIoCompletionPort, GetQueuedCompletionStatus, OVERLAPPED,
 };
 
-// In windows-sys 0.52 `HANDLE` is `isize`. NULL handles are 0; the wrapper
-// uses the constant below for readability.
-const NULL_HANDLE: HANDLE = 0;
+// In windows-sys 0.61 `HANDLE` is `*mut c_void`. NULL handles are null
+// pointers; the wrapper uses the constant below for readability.
+const NULL_HANDLE: HANDLE = std::ptr::null_mut();
 
 /// Owning wrapper around an IOCP `HANDLE`. Closed on drop.
 pub(crate) struct PortHandle {