Add ScreenRecoveryUI::ShowMenu().

From caller's PoV, RecoveryUI::{Start,Select,End}Menu should always be
used together, i.e. to show a menu and get user's selection. This CL
provides ShowMenu() as one-stop service (which is based on
get_menu_selection() from recovery.cpp).

Also move RecoveryUI::{Start,Select,End}Menu into ScreenRecoveryUI, with
a dropped access level from public to protected.

Due to the dependency on recovery / librecovery refactoring, will add
testcases in follow-up CLs.

Test: Build and boot into recovery image. Check the menus (main menu,
      'View recovery logs', 'Wipe data/factory reset').
Change-Id: Ie17aa78144871a12affd6f9075e045f76608a0ba
diff --git a/wear_ui.h b/wear_ui.h
index 8b24cb7..fcbbee2 100644
--- a/wear_ui.h
+++ b/wear_ui.h
@@ -25,9 +25,6 @@
 
   void SetStage(int current, int max) override;
 
-  void StartMenu(const char* const* headers, const char* const* items,
-                 int initial_selection) override;
-
  protected:
   // progress bar vertical position, it's centered horizontally
   const int kProgressBarBaseline;
@@ -36,6 +33,9 @@
   // Recovery, build id and etc) and the bottom lines that may otherwise go out of the screen.
   const int kMenuUnusableRows;
 
+  void StartMenu(const char* const* headers, const char* const* items,
+                 int initial_selection) override;
+
   int GetProgressBaseline() const override;
 
   void update_progress_locked() override;