For #26314 - added migration of tank.bat/tank binaries to core upgrader

- This is essentially the same code from previous migrations but with an extra check to ensure that the tank.bat/tank scripts are only updated for pipeline configs that share the same core.
- Also updated script to use sgtk/Toolkit instead of tank where appropriate (You can ignore these changes - sorry for the pollution!)
I don't think I need the umask (as it's just copying over existing files, not creating new ones) - I'm definitely not a umask expert though..! - what do you think?

I've added the chmod before the copy though to make sure it's writable.