Fix 3.14 beta break with _handle on thread (#1895)

Author: rchiodo

src/debugpy/_vendored/pydevd/_pydev_bundle/pydev_is_thread_alive.py

@@ -5,6 +5,10 @@
 # It is required to debug threads started by start_new_thread in Python 3.4
 _temp = threading.Thread()
 
+if hasattr(_temp, "_os_thread_handle"): # Python 3.14 and later has this
+    def is_thread_alive(t):
+        return not t._os_thread_handle.is_done()
+
 if hasattr(_temp, "_handle") and hasattr(_temp, "_started"):  # Python 3.13 and later has this
 
     def is_thread_alive(t):

src/debugpy/_vendored/pydevd/_pydevd_sys_monitoring/_pydevd_sys_monitoring.py

@@ -13,6 +13,7 @@
 from os.path import basename, splitext
 
 from _pydev_bundle import pydev_log
+from _pydev_bundle.pydev_is_thread_alive import is_thread_alive as pydevd_is_thread_alive
 from _pydevd_bundle import pydevd_dont_trace
 from _pydevd_bundle.pydevd_constants import (
     IS_PY313_OR_GREATER,
@@ -267,7 +268,7 @@ def is_thread_alive(self):
         if self._use_is_stopped:
             return not self.thread._is_stopped
         else:
-            return not self.thread._handle.is_done()
+            return pydevd_is_thread_alive(self.thread)
 
 
 class _DeleteDummyThreadOnDel: