Add a warning for when the scene root node is transformed

[aaronfranke]

This is a low priority PR, but I think it's a good idea.

This PR adds a configuration warning for when the root node has a transform. This is usually a mistake when saving a branch as a scene, or having the wrong node selected when doing transform operations. Instances of the scene will set their own transform, so it's best practice to not have the root be transformed.

[Scoppio]

Tested locally, running fine.

I always miss the presence of GUID or some other unique identification on which is the object that generated the warning, but in this case it seens to be pretty much on topic here.

[Calinou]

The first commit in this PR is just code organization. It does not make much sense for the configuration warning string formatting to be in Node, since this is only needed in the editor.

Note that this may change if we do decide to print node configuration warnings in a running project (when debugging is enabled). This is something I've considered at some point, as it can help with difficult-to-diagnose runtime-only issues without requiring code duplication. See godotengine/godot-proposals#3004.

[ryevdokimov]

I'm personally not a fan of this. I believe warnings should be reserved for when the configuration of a node results in behavior that in all circumstances is not correct (like a collision without a node that derives from it). I don't see anything objectively wrong with changing the transforms of a root node, as long as instantiations of it are handled correctly such as in the above-mentioned PR.

[KoBeWi]

The warning isn't entirely correct. Most often only position is overriden, e.g. when dropping the scene into viewport.

[aaronfranke]

The warning isn't entirely correct. Most often only position is overriden, e.g. when dropping the scene into viewport.

I would argue that if users want a scene to have inherent scale or rotation, they should instead scale or rotate the child nodes. This way this inherent scale or rotation will not be discarded if the user sets node.transform.

If a user sets a scene's scale to be (2, 2, 2), it's expected that the scene should get bigger by a factor of 2. If the original scene had a root node scale of (10, 10, 10), this would result in the scene getting smaller by a factor of 5.

[KoBeWi]

Isn't this (at least partially) superseded by #80561?

[aaronfranke]

@KoBeWi They are separate things, but you are correct that there is a partial overlap. However, this PR covers the case of a user accidentally transforming their scene's root node.