Reset harvest data in unload_data

Harvest data from the previously loaded world was not reset, leading to
a bunch of errors from unrelated mods in a different world.

Add a harvest_list::reset() method to clear the previously loaded
harvest list, and call it from unload_data().

Fix CleverRaven#47932

src/harvest.cpp

@@ -154,6 +154,11 @@ void harvest_list::check_consistency()
     }
 }
 
+void harvest_list::reset()
+{
+    harvest_list_factory.reset();
+}
+
 std::list<harvest_entry>::const_iterator harvest_list::begin() const
 {
     return entries().begin();

src/harvest.h

@@ -88,6 +88,8 @@ class harvest_list
 
         /** Check consistency of all loaded harvest data */
         static void check_consistency();
+        /** Reset all loaded harvest data */
+        static void reset();
 
         bool was_loaded = false;
         void load( const JsonObject &obj, const std::string & );

src/init.cpp

@@ -531,6 +531,7 @@ void DynamicDataLoader::unload_data()
     fault::reset();
     field_types::reset();
     gates::reset();
+    harvest_list::reset();
     item_controller->reset();
     json_flag::reset();
     mapgen_palette::reset();