Revert "bpo-30860: Consolidate stateful runtime globals." (#3379)

Windows buildbots started failing due to include-related errors.
diff --git a/Python/thread_nt.h b/Python/thread_nt.h
index 2f3a71b..47eb4b6 100644
--- a/Python/thread_nt.h
+++ b/Python/thread_nt.h
@@ -189,10 +189,9 @@
         return PYTHREAD_INVALID_THREAD_ID;
     obj->func = func;
     obj->arg = arg;
-    PyThreadState *tstate = PyThreadState_GET();
-    size_t stacksize = tstate ? tstate->interp->pythread_stacksize : 0;
     hThread = (HANDLE)_beginthreadex(0,
-                      Py_SAFE_DOWNCAST(stacksize, Py_ssize_t, unsigned int),
+                      Py_SAFE_DOWNCAST(_pythread_stacksize,
+                                       Py_ssize_t, unsigned int),
                       bootstrap, obj,
                       0, &threadID);
     if (hThread == 0) {
@@ -333,13 +332,13 @@
 {
     /* set to default */
     if (size == 0) {
-        PyThreadState_GET()->interp->pythread_stacksize = 0;
+        _pythread_stacksize = 0;
         return 0;
     }
 
     /* valid range? */
     if (size >= THREAD_MIN_STACKSIZE && size < THREAD_MAX_STACKSIZE) {
-        PyThreadState_GET()->interp->pythread_stacksize = size;
+        _pythread_stacksize = size;
         return 0;
     }