Fine tune search history UX and a11y

1. Show search history after the user clicked clear button on SearchView
2. Add content description on history delete button.
3. Add test and also fix related UI test fail.

Fix: 128889445
Test: manual
Test: atest DocumentsUIGoogleTests:
      com.android.documentsui.SearchViewUiTest#testSearch_NoResults
Change-Id: Id91bebca9f1eba6a8b890519f2f83b4348ca8538