Make os.fchdir, os.fsync, and os.fdatasync accept FileDescriptorLike (#4544)

For the fd passed to these functions, CPython accepts not just an int,
but also anything with a fileno() method.

Fixes #4539

stdlib/3/os/__init__.pyi

@@ -1,5 +1,13 @@
 import sys
-from _typeshed import AnyPath, OpenBinaryMode, OpenBinaryModeReading, OpenBinaryModeUpdating, OpenBinaryModeWriting, OpenTextMode
+from _typeshed import (
+    AnyPath,
+    FileDescriptorLike,
+    OpenBinaryMode,
+    OpenBinaryModeReading,
+    OpenBinaryModeUpdating,
+    OpenBinaryModeWriting,
+    OpenTextMode,
+)
 from builtins import OSError as error
 from io import BufferedRandom, BufferedReader, BufferedWriter, FileIO, TextIOWrapper as _TextIOWrapper
 from posix import listdir as listdir, times_result
@@ -489,7 +497,7 @@ else:
     def dup2(fd: int, fd2: int, inheritable: bool = ...) -> None: ...
 
 def fstat(fd: int) -> stat_result: ...
-def fsync(fd: int) -> None: ...
+def fsync(fd: FileDescriptorLike) -> None: ...
 def lseek(__fd: int, __position: int, __how: int) -> int: ...
 def open(path: AnyPath, flags: int, mode: int = ..., *, dir_fd: Optional[int] = ...) -> int: ...
 def pipe() -> Tuple[int, int]: ...
@@ -500,7 +508,7 @@ if sys.platform != "win32":
     def fchmod(fd: int, mode: int) -> None: ...
     def fchown(fd: int, uid: int, gid: int) -> None: ...
     if sys.platform != "darwin":
-        def fdatasync(fd: int) -> None: ...  # Unix only, not Mac
+        def fdatasync(fd: FileDescriptorLike) -> None: ...  # Unix only, not Mac
     def fpathconf(__fd: int, __name: Union[str, int]) -> int: ...
     def fstatvfs(__fd: int) -> statvfs_result: ...
     def ftruncate(__fd: int, __length: int) -> None: ...
@@ -551,7 +559,7 @@ def access(
 def chdir(path: _FdOrAnyPath) -> None: ...
 
 if sys.platform != "win32":
-    def fchdir(fd: int) -> None: ...
+    def fchdir(fd: FileDescriptorLike) -> None: ...
 
 def getcwd() -> str: ...
 def getcwdb() -> bytes: ...