Add export settings to the export dialog for GLTF

[aaronfranke]

Implements godotengine/godot-proposals#7259 Draft because this depends on #79267, #79313, and #79314 to be merged first all of those are now merged, now this PR is undrafted.

This PR adds export settings to the GLTF export dialog. This dialog allows users to adjust the copyright and image format settings, more can be added in the future.

Additionally, GLTFDocumentExtensions can add new settings to this menu by using @export var like so:

This feature is inspired by the Blender export menu:

Implementation details:

• A new class SceneExporterGLTFSettings is added that overrides the get and set methods and the get property list method to provide a simple interface for accessing settings.
• This new class is edited by EditorInspector which only shows the relevant properties.
• The existing methods in SceneExporterGLTFPlugin have been renamed, they were very confusing before, and they are reordered to be top-to-bottom following their execution order.

[lyuma]

I think it looks good. A couple small comments.

[fire]

Any comments from the production team on next steps?

[lyuma]

texture format None doesn't work:

ERROR: GLTF: Unknown image format 'None'.
   at: (modules\gltf\gltf_document.cpp:3104)
ERROR: glTF2 save scene error 1.
   at: SceneExporterGLTFPlugin::_export_scene_as_gltf (modules\gltf\editor\editor_scene_exporter_gltf_plugin.cpp:116)

[aaronfranke]

@lyuma I'm not able to reproduce that problem on my end. If I make a cube, give it a material with a texture, and export that with the image format set to None, there is no error printed in the output, the export succeeds, and the file has no images.

[lyuma]

The difference is probably that my object has normal, roughness and albedo textures.

The check for None only protects the albedo texture, but the if (has_ao || has_roughness || has_metalness) { if statement for the ORM map doesn't check for None.

Also I'm a little worried that other extensions might choose to add their own textures (such as VRM + MToon) and those might also fail for the same reason.

[aaronfranke]

@lyuma Good catch, you are right, it was not working for non-albedo textures. I updated the code to ensure there is a check before every call to the _set_texture internal helper method. I tested exporting an object with normal and emission and now it works while before it was broken.

[akien-mga]

Thanks!