Fix stopping scripts in the script editor
Check script editor file for external changes when editor regains focus

Prompt user whether to reload changed files.
Add checkbox for automatically reloads externally changed files
Merge branch '19789' into 19803
Fix erroneous "reload script?" prompts in external editor
Reload script into current script engine if script is running

Per manual editing behaviour and keeps the "run" button state in sync.
Fix erroneous "reload?" prompts in external editor with auto reload