Add CoreLib helper used by DefaultValueAttribute constructor

src/System.ComponentModel.TypeConverter/src/ILLinkTrim.xml

@@ -0,0 +1,8 @@
+<linker>
+  <assembly fullname="System.ComponentModel.TypeConverter">
+    <type fullname="System.ComponentModel.TypeDescriptor">
+      <!-- called through reflection by System.ComponentModel.DefaultValueAttribute -->
+      <method name="ConvertFromInvariantString" />
+    </type>
+  </assembly>
+</linker>

src/System.ComponentModel.TypeConverter/src/System/ComponentModel/TypeDescriptor.cs

@@ -808,6 +808,12 @@ public static TypeConverter GetConverter(Type type)
             return GetDescriptor(type, nameof(type)).GetConverter();
         }
 
+        // This is called by System.ComponentModel.DefaultValueAttribute via reflection.
+        private static object ConvertFromInvariantString(Type type, string stringValue)
+        {
+            return GetConverter(type).ConvertFromInvariantString(stringValue);
+        }
+
         /// <summary>
         /// Gets the default event for the specified type of component.
         /// </summary>