Add fcntl.F_DUPFD_QUERY on Linux (#16436)

Python 3.14 exposes `F_DUPFD_QUERY` in `fcntl` on Linux, but the stub
did not declare it, so type checkers rejected its use.

- Declare it for Python 3.14 and later on Linux
- Allowlist it as optional for stubtest, since the GitHub Actions
  runners build against a glibc that lacks the macro

Author: anistark

stdlib/@tests/stubtest_allowlists/linux.txt

@@ -23,6 +23,7 @@ curses.COLOR_PAIRS  # Initialized after start_color
 curses.COLS  # Initialized only after initscr call
 curses.LINES  # Initialized only after initscr call
 fcntl.I_[A-Z0-9_]+  # Platform differences that cannot be captured by the type system
+(fcntl.F_DUPFD_QUERY)?  # Depends on the glibc version Python was built against
 multiprocessing.popen_spawn_win32  # exists on Linux but fails to import
 select.poll  # Actually a function; we have a class so it can be used as a type
 

stdlib/fcntl.pyi

@@ -121,6 +121,9 @@ if sys.platform != "win32":
         RWH_WRITE_LIFE_LONG: Final = 4
         RWH_WRITE_LIFE_EXTREME: Final = 5
 
+    if sys.version_info >= (3, 14) and sys.platform == "linux":
+        F_DUPFD_QUERY: Final[int]
+
     if sys.version_info >= (3, 11) and sys.platform == "darwin":
         F_OFD_SETLK: Final = 90
         F_OFD_SETLKW: Final = 91