*: add "noexcept" to many, many function prototypes

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

src/storage/Configured.hxx

@@ -40,6 +40,6 @@ CreateConfiguredStorage(EventLoop &event_loop);
  */
 gcc_const
 bool
-IsStorageConfigured();
+IsStorageConfigured() noexcept;
 
 #endif