[DocsUI] Attempt to make sidebar bot more stable

* Lift all layout check methods to the base bot level so every
  bot can access those.
* Be more explicit in SidebarBot for openDrawer and findRoot:
  * only open drawer in drawer layout.
  * use the actual id instead of regular expression match when
    searching the root_list inside certain containers.
  * add the content description for the hamburger menu, because the
    "back button" when search is active in the drawer layout matches the
    same previous selector "image button inside toolbar".
* Rename isNavRailLayout to inNavRailLayout for consistency.

Bug: 406924452, 427610294
Test: atest DocumentsUIGoogleTests:com.android.documentsui.SidebarUiTest#testPasteIntoFolderOnRoot
Flag: EXEMPT test code
Change-Id: I394148a722e7b4668d795a8e0216fe1811b383ea