Adding components to an instance of a prefab with slots crashes world (de)serialization

[WouterHunter]

Describe the bug
Adding a component to an instance of a prefab with slots causes ecs_world_to_json to serialize in the wrong order, Calling ecs_world_from_json with the resulting JSON file causes a crash in flecs_name_index_ensure after attempting to register a conflicting entity.

To Reproduce
The following example demonstrates the issue. Removing the line that adds the Rotation component prevents the crash from happening.

namespace Example
{
	struct Position { float x; };
	struct Rotation { float a; };
	struct Turret {
		struct Base {};
		struct Head {};
	};

	struct Module {
		Module(flecs::world& world) {
			// Register example components
			world.component<Position>().member("x", &Position::x);
			world.component<Rotation>().member("a", &Rotation::a);

			// Register prefab and slots
			world.prefab<Turret>().set<Position>({ 1.0f });
			world.prefab<Turret::Base>().slot_of<Turret>();
			world.prefab<Turret::Head>().slot_of<Turret>();
		}
	};
}

int main() {
	flecs::world world_a;
	world_a.import<Example::Module>();

	// Create prefab instance
	flecs::entity inst_a = world_a.entity("my_turret").is_a<Example::Turret>();
	std::cout << inst_a.target<Example::Turret::Base>().path() << std::endl;

	inst_a.add<Example::Rotation>(); // <-- Adding another component is the issue

	// Serialize world to JSON
	auto json = world_a.to_json();
	std::cout << json << std::endl;

	// Create second world, import same module and deserialize
	flecs::world world_b;
	world_b.import<Example::Module>();
	world_b.from_json(json); // <-- crash
	
	// Error message:
	//	fatal: flecs.c: 31912: abort(): conflicting entity registered with 
	//	name 'Base' (existing = 584, new = 586) (ALREADY_DEFINED)

	flecs::entity inst_b = world_b.lookup("my_turret");
	std::cout << inst_b.target<Example::Turret::Base>().path() << std::endl;
}

Expected behavior
I'd expect that adding components to prefab instances wouldn't be an issue, whether that prefab uses slots or not. I can work around this problem, but I'd like to use prefab slots and this issue currently prevents me from doing so.

Additional context
I tested this on the latest version of the master branch.

[WouterHunter]

The problem doesn't just appear with prefab slots, but with prefab-inherited child entities in general. Removing the .slot_of<Turret>() statements still causes a crash like in the original example:

namespace Example {
	struct Position { float x; };
	struct Rotation { float a; };
	
	struct Turret {
		struct Base {};
		struct Head {};
	};

	struct Module {
		Module(flecs::world& world) {
			// Register example components
			world.component<Position>().member("x", &Position::x);
			world.component<Rotation>().member("a", &Rotation::a);

			// Register prefab and slots
			world.prefab<Turret>().set<Position>({ 1.0f });
			world.prefab<Turret::Base>();
			world.prefab<Turret::Head>();
		}
	};
}

int main() {
	flecs::world world_a;
	world_a.import<Example::Module>();

	// Create prefab instance
	flecs::entity inst_a = world_a.entity("my_turret").is_a<Example::Turret>();
	std::cout << inst_a.lookup("Base").path() << std::endl;

	inst_a.add<Example::Rotation>(); // <-- Adding another component is the issue

	// Serialize world to JSON
	auto json = world_a.to_json();
	std::cout << json << std::endl;

	// Create second world, import same module and deserialize
	flecs::world world_b;
	world_b.import<Example::Module>();
	world_b.from_json(json); // <-- crash
	
	// Error message:
	//	fatal: flecs.c: 31912: abort(): conflicting entity registered with 
	//	name 'Base' (existing = 584, new = 586) (ALREADY_DEFINED)

	flecs::entity inst_b = world_b.lookup("my_turret");
	std::cout << inst_b.lookup("Base").path() << std::endl;
}

Could be that this is related to issue #1498