Add empty view in PhotoPicker

- Use the device default theme
- Support empty view in AutoFitRecyclerView
- Add empty view in TabFragment

Test: video on the bug
Test: atest NoItemsTest
Bug: 195913683

Change-Id: Ifedcc3a3deb529ce613e98fdbc8c8391e7fe57c6
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index e85c2ba..88fbe53 100644
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -59,6 +59,9 @@
     <dimen name="picker_drag_margin_top">8dp</dimen>
     <dimen name="picker_drag_margin_bottom">12dp</dimen>
 
+    <dimen name="picker_empty_text_margin">20dp</dimen>
+    <dimen name="picker_empty_text_size">18sp</dimen>
+
     <!-- PhotoPicker Preview -->
     <dimen name="preview_buttons_padding_horizontal">16dp</dimen>
     <dimen name="preview_deselect_padding_start">2dp</dimen>