Add color processing system to theme json

[schlotterer]

This PR applies some build lessons to the theme.json.
Primarily this update adds a custom section to the json that will allow us to create an css vars we want (colors and more) without having to add a million colors to the pallet in the admin. This update separate the need for css color vars to work with in the theme and the need for a color pallet in the admin that is curated for the end user.
This update also takes advantage of the color-mix css property to dynamically build color variations and allow for faster scaffolding.
This update also cleaned up some color vars that were being used in the markup but were never set.

What type of PR is this? (put an x to all applicable)

• [ x] 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation Update
• [x ] 🎨 Style
• [ x] 🧑‍💻 Code Refactor
• 🔥 Performance Improvements
• ✅ Test
• 🤖 Build
• 🔁 CI
• 📦 Chore (Release)
• ⏩ Revert

Mobile & Desktop Screenshots/Recordings

Added tests?

• 👍 yes
• [x ] 🙅 no, because they aren't needed
• 🙋 no, because I need help

Added to documentation?

• 📜 README.md
• 📓 Confluence
• [ x] 🙅 no documentation needed