Code Quality: Modernize solution structure

[Lamparter]

📄 Description

Modernise the structure with .NET Runtime inspired configuration. This involves a build engine folder, MSBuild properties files, a source directory, and more organisation in a similar way to the folder structure of Files and the .NET Runtime

🥽 Concerned code

All projects

✨ Gains

• Better understanding
• Cleaner codebase
• More professional outlook

📋 Requirements

• src: source code
  • core
  • platforms
  • ..idk about these subfolders
• tests: tests
• eng: build files and packaging project

📸 Assets

• Files
• IronPython
• Rosetta
• .NET

[Lamparter]

literally copied straight from RiversideValley/Graphite#41
I am going to copy this issue to other places where it is necessary