Fix particle spawners not visible since CSM spawner implementation (#8289)

* Drop the ID mapper, use a big u64 instead. This will permit to resync server ids properly with the manager code
* Modernize some code parts (std::unordered_map, auto)
* generate id on client part on U32_MAX + 1 ids, lower are for server ids

src/client/client.h

@@ -565,9 +565,6 @@ private:
 	// And relations to objects
 	std::unordered_map<int, u16> m_sounds_to_objects;
 
-	// CSM/client IDs to SSM/server IDs Mapping
-	// Map server particle spawner IDs to client IDs
-	std::unordered_map<u32, u32> m_particles_server_to_client;
 	// Map server hud ids to client hud ids
 	std::unordered_map<u32, u32> m_hud_server_to_client;