Delete pure properties :(

[nth-commit]

Why?

• Lots of code (and hacks to work)
• Reflected properties are much easier to configure since MemberGenAttribute
• Want to encourage using the default conventions and generators as much as possible, so users get the best devx with a refined experience
• SelectMany is inherently less performant
• They take up too much real-estate in the root namespace, Test/AsyncTest variants and helpers all need to be in the namespace to make them useful