Fix AnimationPlayer finished state in the editor

[TokageItLab]

• Fixes AnimationPlayer animation skips to the beginning and changes the values when finished in the editor #106095
• Supersedes/Closes Fix Animation Editor skips to 1th frame when stopped. #107010

Avoid resetting by determining the case based on the signal when the timeline ends.

[fire]

State machines tend to be convoluted so I hope it works without systematically diagramming and looking for missing cases. Approved.

[akien-mga]

Thanks!