refs https://linear.app/tryghost/issue/CORE-35/refactor-route-and-redirect-settings
- This is a micro-step towards getting rid of multiple "knownSettings" concept. Since the introduction of an array of knowSettings there was never-ever a need to handle anything but a single `routes.yaml` file. Getting rid of this concept first to have a simpler module. Next step would be getting rid of filesystem reads/writes in the "frontend"