### 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)

for (uint32_t j = 0; j < 4; j++) {
				Vector3 p = p_points[p_simplices[p_simplex_indices[i]].vertices[j]];
				if (j == 0) {
					bounds.position = p;
				} else {
					bounds.expand_to(p);
				}
			}
			if (i == 0) {
				centers.push_back(bounds.get_center());
			} else {
				bounds_all.merge_with(bounds);
			}
		}
		Vector3::Axis longest_axis = Vector3::Axis(bounds_all.get_longest_axis_index());
		
		uint32_t min_d_idx = 0xFFFFFFFF;
		float min_d_dist = 1e20;
		for (uint32_t i = 0; i < centers.size(); i++) {
			if (centers[i][longest_axis] < min_d_dist) {
				min_d_idx = i;
				min_d_dist = centers[i][longest_axis];
			}
		}
		
		best_plane = Plane();
		best_plane.normal[longest_axis] = 1.0;
		best_plane.d = min_d_dist;
		indices_under.clear();
		indices_under.push_back(min_d_idx);