Make widget pickers edit text box parent focusable.

This is so that when focus is cleared from edit text box, the focus
fallbacks to parent view when external keyboard is used.

Bug: b/197129170
Test: Manually checked that behavior is okay when widget picker and
search is used with and without keyboard. Manually checked talkback
navigation is ok.

Change-Id: Iec2e1ff183dae20803ba2f6eb6e260d2a57779b8
diff --git a/res/layout/widgets_full_sheet.xml b/res/layout/widgets_full_sheet.xml
index 0fc0ff8..309dc42 100644
--- a/res/layout/widgets_full_sheet.xml
+++ b/res/layout/widgets_full_sheet.xml
@@ -25,7 +25,9 @@
         android:id="@+id/container"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:background="@drawable/bg_widgets_full_sheet">
+        android:background="@drawable/bg_widgets_full_sheet"
+        android:focusable="true"
+        android:importantForAccessibility="no">
 
         <View
             android:id="@+id/collapse_handle"