### Godot version

4.0 beta 17

### System information

Windows 11, Forward+, RTX 4090

### Issue description

In the latest beta, baking LightmapGI has taken a big performance hit. The baking itself might not be the problem, it's the (Re)Importing Assets step for the `.exr` that seems to take all the time.




### Steps to reproduce

I've included a repro project to demonstrate it. Click the `LightmapGI` node and then the `Bake Lightmaps` button.

Before Beta 17:
`Done baking lightmaps in 00:00:01.`

With Beta 17 (and the latest Master branch, just in case):
`Done baking lightmaps in 00:00:08.`



### Minimal reproduction project

[lightmap-regression-repro.zip](https://github.com/godotengine/godot/files/10579835/lightmap-regression-repro.zip)

int32_t node_index = (int32_t)bsp_nodes.size();
	bsp_nodes.push_back(BSPNode());
	
	Plane best_plane;
	float best_plane_score = -1.0;
	for (const int idx : p_simplex_indices) {
		const BSPSimplex &s = p_simplices[idx];
		for (int j = 0; j < 4; j++) {
			uint32_t plane_index = s.planes[j];
			if (planes_tested[plane_index] == node_index) {
				continue; 
			}
			planes_tested[plane_index] = node_index;
			static const int face_order[4][3] = {
				{ 0, 1, 2 },
				{ 0, 2, 3 },
				{ 0, 1, 3 },
				{ 1, 2, 3 }
			};
			
			
			Vector3 v0 = p_points[s.vertices[face_order[j][0]]];
			Vector3 v1 = p_points[s.vertices[face_order[j][1]]];
			Vector3 v2 = p_points[s.vertices[face_order[j][2]]];
			Plane plane(v0, v1, v2);
			
			int over_count = 0;
			int under_count = 0;
			for (const int &index : p_simplex_indices) {