creator.onOpenFileChooser - Introduce a parameter which would indicate the source property

[JaneSjs]

T16988 - Custom Dialog for File Choose https://surveyjs.answerdesk.io/internal/ticket/details/T16988

Please introduce an additional parameter within the creator.onOpenFileChooser event. The parameter should indicate a source property for which a user activates a file open dialog. A usage scenario - customize the open file dialog for a Theme Tab -> a survey background image property.