Support for saving multiple Images in BakedLightmap is not implemented properly

[gdlq]

Godot version

3.5RC2

System information

Windows 10, GLES3

Issue description

I can’t believe I have to do this again…
In previous issue #61547 I explain a problem with inability to bake multi-image atlases, no matter what I do it bakes all in one single atlas (or worse it didn’t bake at all).

@JFonS explained that this happens because of the very large mesh, so this time I removed that mesh from MRP and kept only standard cubes imported from Blender.
Lightmap scale is set to 4x, Atlas Size is 2048 and yet it bakes all in single absurdly large 2048х12288 atlas!
And if you set lightmap scale to 1x it still bakes single lightmap as 512x3072, which doesn't make any sense because we set 2048 in Atlas Size.
Issue #58102 seems to be implemented incorrectly and doesn't create multiple baked .exr lightmap textures.

Steps to reproduce

Bake lightmaps from minimal reproduction project.

Minimal reproduction project

test_lightmap_large_3.x.zip

[JFonS]

Duplicate of #61547, answered there.