Introduce a Switch on Node Group script node

[Naros]

Description

In a scene, users can define groups (scene level or global/project level). These groups are descriptive tags that can be applied to one or more nodes and are often used for various game play mechanics. It would be helpful to introduce a node that branches based on group, perhaps with the Node as the input.

Implementation ideas

For global groups, this is fairly simple as they're managed within the Godot project.

This gets to be trickier with scene-level groups, because we either need to rely on the SceneTree::get_current_edited_scene or somehow encode a scene file reference into the node, using a load of the PackedScene to get the groups when it isn't opened. We'll need to investigate the trade-offs and issues as the groups need to dynamically update as a user adds/removes groups.