pythongh-118392: Add warning about random.random for multi thread app

Author: corona10

Doc/library/random.rst

@@ -294,6 +294,10 @@ be found in any statistics text.
 
    Return the next random floating point number in the range ``0.0 <= X < 1.0``
 
+   .. warning::
+      Directly calling this function in a multithreaded application can cause the
+      performance degradation. Instead, use the :class:`Random` per thread.
+
 
 .. function:: uniform(a, b)