gh-109700: Improve stress tests for interpreter creation (GH-109946)

* Ensure that destructors are called in the test that created interpreters, not after finishing it.
* Try to create/run interpreters in threads simultaneously.
* Mark tests that requires over 6GB of memory with bigmemtest.

Lib/test/test_interpreters/test_stress.py

@@ -21,21 +21,29 @@ def test_create_many_sequential(self):
         for _ in range(100):
             interp = interpreters.create()
             alive.append(interp)
+        del alive
+        support.gc_collect()
 
-    @support.requires_resource('cpu')
-    @threading_helper.requires_working_threading()
-    def test_create_many_threaded(self):
+    @support.bigmemtest(size=200, memuse=32*2**20, dry_run=False)
+    def test_create_many_threaded(self, size):
         alive = []
+        start = threading.Event()
         def task():
+            # try to create all interpreters simultaneously
+            if not start.wait(support.SHORT_TIMEOUT):
+                raise TimeoutError
             interp = interpreters.create()
             alive.append(interp)
-        threads = (threading.Thread(target=task) for _ in range(200))
+        threads = [threading.Thread(target=task) for _ in range(size)]
         with threading_helper.start_threads(threads):
-            pass
+            start.set()
+        del alive
+        support.gc_collect()
 
-    @support.requires_resource('cpu')
     @threading_helper.requires_working_threading()
-    def test_many_threads_running_interp_in_other_interp(self):
+    @support.bigmemtest(size=200, memuse=34*2**20, dry_run=False)
+    def test_many_threads_running_interp_in_other_interp(self, size):
+        start = threading.Event()
         interp = interpreters.create()
 
         script = f"""if True:
@@ -47,6 +55,9 @@ def run():
             interp = interpreters.create()
             alreadyrunning = (f'{interpreters.InterpreterError}: '
                               'interpreter already running')
+            # try to run all interpreters simultaneously
+            if not start.wait(support.SHORT_TIMEOUT):
+                raise TimeoutError
             success = False
             while not success:
                 try:
@@ -58,9 +69,10 @@ def run():
                 else:
                     success = True
 
-        threads = (threading.Thread(target=run) for _ in range(200))
+        threads = [threading.Thread(target=run) for _ in range(size)]
         with threading_helper.start_threads(threads):
-            pass
+            start.set()
+        support.gc_collect()
 
 
 if __name__ == '__main__':