Get "stopped" back into repr(Thread) when appropriate.

Due to recent changes, a Thread doesn't know that it's over before
someone calls .join() or .is_alive().  That meant repr(Thread)
continued to include "started" (and not "stopped") before one of
those methods was called, even if hours passed since the thread
ended.

Repaired that.

Lib/threading.py

@@ -574,6 +574,7 @@ class Thread:
         status = "initial"
         if self._started.is_set():
             status = "started"
+        self.is_alive() # easy way to get ._is_stopped set when appropriate
         if self._is_stopped:
             status = "stopped"
         if self._daemonic: