[Ada] Fix crash on type extensions with discriminants

[Pierre-Marie de Rodat]

In Ada 2022 mode, the compiler crashes when generating the Put_Image
function for a tagged type if the parent subtype is constrained.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * exp_put_image.adb (Make_Component_Attributes): Use
        Implementation_Base_Type to get the parent type. Otherwise,
        Parent_Type_Decl is actually an internally generated subtype
        declaration, so we blow up on
        Type_Definition (Parent_Type_Decl).
diff --git a/gcc/ada/exp_put_image.adb b/gcc/ada/exp_put_image.adb
--- a/gcc/ada/exp_put_image.adb
+++ b/gcc/ada/exp_put_image.adb
@@ -658,8 +658,8 @@ package body Exp_Put_Image is
                   if Chars (Defining_Identifier (Item)) = Name_uParent then
                      declare
                         Parent_Type : constant Entity_Id :=
-                          Underlying_Type (Base_Type (
-                            (Etype (Defining_Identifier (Item)))));
+                          Implementation_Base_Type
+                            (Etype (Defining_Identifier (Item)));
 
                         Parent_Aspect_Spec : constant Node_Id :=
                           Find_Aspect (Parent_Type, Aspect_Put_Image);