Fix doubly-reserved unique names in GLTF scene name assignment

[aaronfranke]

This PR has 2 related but technically independent bugfixes. I could separate them but I figured I'd just make one PR. These fixes very slightly change behavior, so do not cherry-pick this to 4.1.x, but it's good for 4.2.

1. Fix double reserving of node names for nodes without a name in _assign_node_names. Test file:

{
	"asset": { "version": "2.0" },
	"nodes": [{}],
	"scene": 0,
	"scenes": [{ "nodes": [0] }]
}

Behavior in master:

Behavior in this PR:

2. Fix scene names in _parse_scenes reserving as priority over node names and breaking node names. Test file:

{
	"asset": { "version": "2.0" },
	"nodes": [{ "name": "EmptyScene" }],
	"scene": 0,
	"scenes": [{ "nodes": [0], "name": "EmptyScene" }]
}

Behavior in master:

Behavior in this PR:

Note: In the future I do want the scene name to be used as the root node name in some situations. However, in the current master this does not happen, and in the future when we do want this to happen, the current part of the code reserving the name is the wrong place to do it. We want to do it later on so that the actual nodes in the GLTF file have their names take priority, and the names of the nodes Godot generates are secondary.

[fire]

Is there a reason for the name changes? Like Camera3D

[fire]

I don't have a strong opinion on the names, but it is a backwards compatibility change I think.

It's not common to animate cameras or lights, but it's possible.

[fire]

I think the other changes are good, but we're discussing how to arrange the name change.

[fire]

Summary

• Name change from s to scene_dict (no operation / code cleaness)
• Remove _gen_unique_name on the gltf node name

[fire]

		if (s.has("name") && !String(s["name"]).is_empty() && !((String)s["name"]).begins_with("Scene")) {
			p_state->scene_name = _gen_unique_name(p_state, s["name"]);
		} else {
			p_state->scene_name = _gen_unique_name(p_state, p_state->filename);
		}

This part has the _gen_unique_name removed as it was a bug.

There is a rename from s to scene_dict and caching the gltf_node_name.

[akien-mga]

What's the impact on compatibility for scenes imported in 4.1, and with changes to the nodes which would get a rename?

I already had to deal with such a compat breakage between 4.0 and 4.1 in gdquest-demos/godot-4-3d-third-person-controller#30, and that wasn't pretty. We should do our best to avoid breaking projects as far as possible.

[aaronfranke]

@akien-mga I actually tested on that exact project last week. Every node in every GLB file in that project is named, therefore there are no auto-generated names, therefore this PR does not affect that project at all.

I think most people use GLB files exported from Blender, and Blender requires all nodes to have unique names, so this PR should not affect any GLB file exported from Blender.

[akien-mga]

Thanks!