Update StorageSummaryDonutPreference content

- Set its view as unclickable
- Add content discription on DountView

Fixes: 78172416
Fixes: 78170302
Test: manual open talkback to check voice content
Change-Id: Ic40f88fb27344822bbb14cf62a79d8e030ee16ac

src/com/android/settings/widget/DonutView.java

@@ -205,6 +205,8 @@ public class DonutView extends View {
                             .getDimension(
                                     R.dimen.storage_donut_view_shrunken_label_text_size));
         }
+        setContentDescription(getContext().getString(
+                R.string.join_many_items_middle, mPercentString, mFullString));
         invalidate();
     }