New files should not be saved to location until manually saved

[matthijseikelenboom]

Description

This PR changes how new files are created, when they're not created via the project navigator.

Right now, the user is required to first create and save a file before it can be edited. Now it's possible to create an unsaved scratch file, that is deleted when closed empty or has to be saved when the user closes it when there in content in it.

Related Issues

• #1070

Checklist

Subtasks

• [x] Save scratch file to temp location on disk
• [ ] Mark the tab closing indicator unsaved when there is content inside the scratch file
• [ ] Remove the file when it's closed empty

General PR

• [x] I read and understood the contributing guide as well as the code of conduct
• [x] The issues this PR addresses are related to each other
• [ ] My changes generate no new warnings
• [x] My code builds and runs on my machine
• [x] My changes are all related to the related issue above
• [x] I documented my code

Screenshots

(Not yet made)