gh-116126: Implement PEP 696 (#116129)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>

Lib/ast.py

@@ -1124,12 +1124,21 @@ class _Unparser(NodeVisitor):
         if node.bound:
             self.write(": ")
             self.traverse(node.bound)
+        if node.default_value:
+            self.write(" = ")
+            self.traverse(node.default_value)
 
     def visit_TypeVarTuple(self, node):
         self.write("*" + node.name)
+        if node.default_value:
+            self.write(" = ")
+            self.traverse(node.default_value)
 
     def visit_ParamSpec(self, node):
         self.write("**" + node.name)
+        if node.default_value:
+            self.write(" = ")
+            self.traverse(node.default_value)
 
     def visit_TypeAlias(self, node):
         self.fill("type ")