Perform continuous validation

[Naros]

Description

Currently, validation is performed by the user clicking the Validate button or when the Orchestration is open and the EditorPlugin triggers a build step. While this is helpful, it would be better if it happened asynchronously and automatically while the user interacts with the plug-in.

Implementation ideas

Each GraphNode implementation should support adding a ⚠️ icon on each pin that fails validation. This icon could then be toggled on various user actions that cause some problem. A timer task could also run periodically that runs the validation routine and updates these icons accordingly.