DocumentsUI: Fix some test failures in DocumentsUITests

There're some failures on existing DocumentsUI tests. This CL fixes some
of them.

1) KeyboardNavigationUiTest#testKeyboard_arrowsRootsList

-> The initial focused item when TAB key is pressed has been changed and
   roots list gets focus by the second TAB key.

2) SearchViewUiTest#testSearchView_ClearsTextOnBack
3) SearchViewUiTest#testSearchView_CollapsesOnBack

-> Now it requires two times Back key press to exit search mode.

4) RenameDocumentUiTest#testNoRenameSupport_SingleSelection
5) RenameDocumentUiTest#testOneHasRenameSupport_MultipleSelection
6) RenameDocumentUiTest#testRenameDisabled_MultipleSelection

-> The view hieralchy of menu item has been changed. Now
   ListMenuItemView (inherit from LinearLayout) contains LinearLayout
   and it needs to find the ListMenuItemView object when searching
   the target menu item.

Test: Run instrumentation tests from com.android.documentsui.tests
Bug: 77892143
Change-Id: Ic19629ee7421c5a4f44eed80fa564ba376fd61e2
(cherry picked from commit af40f5368137938a568cab52ddd71846f5bb507d)