[DocsUI M3] Add RecyclerView adapter for nav roots

This is the preparation of converting navigation tree from ListView
to RecyclerView (in order to fix the tab cycle problem). The existing
RootsAdapter doesn't work with RecyclerView, so creating this to
replicate the same functionalities.

Bug: 370628223
Test: atest DocumentsUIGoogleTests:com.android.documentsui.sidebar.RecyclerRootsAdapterTest
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ifb18cc50a9ba19f439cf3470214e69687cf385e4