fs: add safe impl From<OwnedFd> for File (#8266)

This impl was missing to be able to create a tokio::fs::File directly
from an OwnedFd, which can be done in a safe way.  Going through RawFd
required unsafe for the same operation.

And same for Windows using a OwnedHandle instead.

tokio/src/fs/file.rs

@@ -897,6 +897,13 @@ impl fmt::Debug for File {
     }
 }
 
+#[cfg(unix)]
+impl From<std::os::fd::OwnedFd> for File {
+    fn from(fd: std::os::fd::OwnedFd) -> Self {
+        Self::from_std(StdFile::from(fd))
+    }
+}
+
 #[cfg(unix)]
 impl std::os::unix::io::AsRawFd for File {
     fn as_raw_fd(&self) -> std::os::unix::io::RawFd {
@@ -923,7 +930,13 @@ impl std::os::unix::io::FromRawFd for File {
 }
 
 cfg_windows! {
-    use crate::os::windows::io::{AsRawHandle, FromRawHandle, RawHandle, AsHandle, BorrowedHandle};
+    use crate::os::windows::io::{AsRawHandle, FromRawHandle, RawHandle, AsHandle, BorrowedHandle, OwnedHandle};
+
+    impl From<OwnedHandle> for File {
+        fn from(handle: OwnedHandle) -> Self {
+            Self::from_std(StdFile::from(handle))
+        }
+    }
 
     impl AsRawHandle for File {
         fn as_raw_handle(&self) -> RawHandle {

tokio/src/fs/mocks.rs

@@ -38,6 +38,10 @@ mock! {
         pub fn try_clone(&self) -> io::Result<Self>;
     }
     #[cfg(windows)]
+    impl From<std::os::windows::io::OwnedHandle> for File {
+        fn from(handle: std::os::windows::io::OwnedHandle) -> Self;
+    }
+    #[cfg(windows)]
     impl std::os::windows::io::AsRawHandle for File {
         fn as_raw_handle(&self) -> std::os::windows::io::RawHandle;
     }