WIP: Added staged files state to IDE

What does this MR do?

Gives the ability for users to stage & unstage changes in the commit sidebar. Users can stage/unstage all the changes in one go or they can do this on an individual file basis.

Staged changes freezes the file at a certain point by copying the object over to a new state location. This gives the ability for users to do more changes & have these changes in unstaged changes. If the user then stages this change it updates the freezed object with the new data. If the user unstages this change it will add it back into the changedFiles array if it doesn't exist, if it does exist then it only removes it from the staged changes array.

Screenshots (if relevant)

What are the relevant issue numbers?

Closes #4541 (moved)