Add getter for presentationProvider in Grid.Column (#10323) (#12060)

Without access to the presentation provider used for a column, it is often not possible to reconstruct the data as shown on the end-user's screen

This commit adds a getter method to Grid.Column to allow access to this provider

server/src/main/java/com/vaadin/ui/Grid.java

@@ -1261,6 +1261,18 @@ public ValueProvider<T, V> getValueProvider() {
             return valueProvider;
         }
 
+        /**
+         * Gets the function to get presentations from the value of data in this
+         * column, based on the row item.
+         *
+         * @return the presentation provider function
+         *
+         * @since
+         */
+        public ValueProvider<V, ?> getPresentationProvider() {
+            return presentationProvider;
+        }
+
         /**
          * Sets whether the user can sort this column or not. Whether the column
          * is actually sortable after {@code setSortable(true)} depends on the