bpo-40422: Move _Py_closerange to fileutils.c (GH-22680)

This API is relatively lightweight and organizationally, given that it's
used by multiple modules, it makes sense to move it to fileutils.

Requires making sure that _posixsubprocess is compiled with the appropriate
Py_BUIILD_CORE_BUILTIN macro.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index de81db8..6ce0bcb 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -22,6 +22,7 @@
 #define PY_SSIZE_T_CLEAN
 
 #include "Python.h"
+#include "pycore_fileutils.h"
 #ifdef MS_WINDOWS
    /* include <windows.h> early to avoid conflict with pycore_condvar.h:
 
@@ -8740,82 +8741,6 @@
     Py_RETURN_NONE;
 }
 
-/* Our selection logic for which function to use is as follows:
- * 1. If close_range(2) is available, always prefer that; it's better for
- *    contiguous ranges like this than fdwalk(3) which entails iterating over
- *    the entire fd space and simply doing nothing for those outside the range.
- * 2. If closefrom(2) is available, we'll attempt to use that next if we're
- *    closing up to sysconf(_SC_OPEN_MAX).
- * 2a. Fallback to fdwalk(3) if we're not closing up to sysconf(_SC_OPEN_MAX),
- *    as that will be more performant if the range happens to have any chunk of
- *    non-opened fd in the middle.
- * 2b. If fdwalk(3) isn't available, just do a plain close(2) loop.
- */
-#ifdef __FreeBSD__
-#define USE_CLOSEFROM
-#endif /* __FreeBSD__ */
-
-#ifdef HAVE_FDWALK
-#define USE_FDWALK
-#endif /* HAVE_FDWALK */
-
-#ifdef USE_FDWALK
-static int
-_fdwalk_close_func(void *lohi, int fd)
-{
-    int lo = ((int *)lohi)[0];
-    int hi = ((int *)lohi)[1];
-
-    if (fd >= hi) {
-        return 1;
-    }
-    else if (fd >= lo) {
-        /* Ignore errors */
-        (void)close(fd);
-    }
-    return 0;
-}
-#endif /* USE_FDWALK */
-
-/* Closes all file descriptors in [first, last], ignoring errors. */
-void
-_Py_closerange(int first, int last)
-{
-    first = Py_MAX(first, 0);
-    _Py_BEGIN_SUPPRESS_IPH
-#ifdef HAVE_CLOSE_RANGE
-    if (close_range(first, last, 0) == 0 || errno != ENOSYS) {
-        /* Any errors encountered while closing file descriptors are ignored;
-         * ENOSYS means no kernel support, though,
-         * so we'll fallback to the other methods. */
-    }
-    else
-#endif /* HAVE_CLOSE_RANGE */
-#ifdef USE_CLOSEFROM
-    if (last >= sysconf(_SC_OPEN_MAX)) {
-        /* Any errors encountered while closing file descriptors are ignored */
-        closefrom(first);
-    }
-    else
-#endif /* USE_CLOSEFROM */
-#ifdef USE_FDWALK
-    {
-        int lohi[2];
-        lohi[0] = first;
-        lohi[1] = last + 1;
-        fdwalk(_fdwalk_close_func, lohi);
-    }
-#else
-    {
-        for (int i = first; i <= last; i++) {
-            /* Ignore errors */
-            (void)close(i);
-        }
-    }
-#endif /* USE_FDWALK */
-    _Py_END_SUPPRESS_IPH
-}
-
 /*[clinic input]
 os.closerange