Repo cleanup: Remove outdated design files and specs

Purpose

This project contains many outdated Sketch, Framer, and spec files that can be removed. Files could still be found through git history. Most files haven't been touched in over 2 years.

• Sketch files → Using Figma for design
• Framer → Not part of the official design stack
• Specs → Using a combination of Figma and GitLab UI to have specs in Pajamas

This will likely be broken into three MRs to make the change reviews easier.

• Remove '/hosted' files !350 (merged).
• Remove '/progress' files !351 (merged).
• Remove misc unused files !352 (merged).