Implement GraphFrame variant for comment nodes

[Naros]

Description

Godot 4.3 introduced a new graph element called GraphFrame, which is ideal for comment nodes. For Orchestrator 2.1, we should aim to move to using GraphFrame rather than our custom implementation.

Implementation ideas

One way to handle the auto-upgrade would be to introduce a new BitField in the Orchestration. When moving to 2.1, the flag would be false, signaling that the editor should automatically link any graph node that overlaps with a frame. Once this step is done, the flag will be set to true so that the auto-link will not happen.

Comment nodes in 2.1 will need to store their linked nodes.
This attribute/property would only be serializable in 2.1, not 2.0.

If an Orchestration that had been saved with 2.1 is opened with 2.0 and re-saved, then the flag and linked nodes to frames will be lost; however, when re-opening the Orchestration with 2.1, the auto-link phase will refire, and nothing will be lost.