gh-137400: Fix a crash when disabling profiling across all threads (gh-137471)

The `PyEval_SetProfileAllThreads` function and other related functions
had a race condition on `tstate->c_profilefunc` that could lead to a
crash when disable profiling or tracing on all threads while another
thread is starting to profile or trace a a call.

There are still potential crashes when threads exit concurrently with
profiling or tracing be enabled/disabled across all threads.

Python/legacy_tracing.c

@@ -477,13 +477,16 @@ setup_profile(PyThreadState *tstate, Py_tracefunc func, PyObject *arg, PyObject
         }
     }
 
+    _PyEval_StopTheWorld(tstate->interp);
     int delta = (func != NULL) - (tstate->c_profilefunc != NULL);
     tstate->c_profilefunc = func;
     *old_profileobj = tstate->c_profileobj;
     tstate->c_profileobj = Py_XNewRef(arg);
     tstate->interp->sys_profiling_threads += delta;
     assert(tstate->interp->sys_profiling_threads >= 0);
-    return tstate->interp->sys_profiling_threads;
+    Py_ssize_t profiling_threads = tstate->interp->sys_profiling_threads;
+    _PyEval_StartTheWorld(tstate->interp);
+    return profiling_threads;
 }
 
 int
@@ -574,13 +577,16 @@ setup_tracing(PyThreadState *tstate, Py_tracefunc func, PyObject *arg, PyObject
         }
     }
 
+    _PyEval_StopTheWorld(tstate->interp);
     int delta = (func != NULL) - (tstate->c_tracefunc != NULL);
     tstate->c_tracefunc = func;
     *old_traceobj = tstate->c_traceobj;
     tstate->c_traceobj = Py_XNewRef(arg);
     tstate->interp->sys_tracing_threads += delta;
     assert(tstate->interp->sys_tracing_threads >= 0);
-    return tstate->interp->sys_tracing_threads;
+    Py_ssize_t tracing_threads = tstate->interp->sys_tracing_threads;
+    _PyEval_StartTheWorld(tstate->interp);
+    return tracing_threads;
 }
 
 int