Integrate Feature-Reactivity With FlexExpressionEditor Node

This pull request introduces a feature-reactivity system for expressions in ComfyUI-AdvancedLivePortrait, allowing expressions to be modulated dynamically by various feature sources. The feature sources supported include **audio, MIDI, motion, proximity, time, depth, color, brightness, pitch, and more**. ### Main Contribution: To implement this system, I have added a new node called the FlexExpressionEditor. This node functions similarly to the existing expression editor but is enhanced to accept feature inputs, enabling expressions to be modulated over time by external sources such as audio. Key features of the FlexExpressionEditor include: **Feature Targets:** any of the expression parameters can be modulated by the feature input **Interchangeable Feature Sources:** Any supported feature source can be applied interchangeably **Chaining Capability:** Multiple FlexExpressionEditor nodes can be chained, enabling complex and layered expression control. #### Benefits: The FlexExpressionEditor adds a powerful dimension to the expression capabilities within this project, providing users with fine-grain control over expressions through external inputs. This enhancement offers substantial new functionality with no impact on the existing features or workflows. #### Additional Information: - To facilitate testing and exploration of this new functionality, I have included two example workflows demonstrating the feature-reactivity system in action. - There is some refactoring that could be done in the ExpressionEditor that I have left pending your review. Thank you for considering this addition. I am open to any feedback or suggestions for further refinement. Using drums to rotate_pitch, synth for pupil_x, and manual feature for rotate_roll: https://github.com/user-attachments/assets/72f95c90-9fa9-4e3e-a492-739566c188c9 Using time feature to modulate aaa and the motion of the driving video to modulate yaw: https://github.com/user-attachments/assets/cc43b439-e089-43c0-8a3e-d9b16467d983 Using proximity to control aaa: https://github.com/user-attachments/assets/828039ef-5d9b-4f93-a818-ae1c1ce31cc9 Using area to control blink: https://github.com/user-attachments/assets/cd383ba7-984a-4c56-a927-ff9fd608e5f8