Reorganize and clean up old settings and configuration

Problem/Motivation

The settings and configuration from this theme are out of date and cleaning them up will improve maintainability and ease of use.

Changes I'm suggesting:

• Adding a schema that captures the settings from this theme. Alternatively, we could try to emulate the much more complicated (but also more sophisticated) settings management that Bootstrap uses, which also updates sub-themes when updates to settings are released. But I don't understand how it works so for now, using Olivero as a model, we could just capture the settings in a schema file.
• Removing respond.js configuration. This is not used anywhere and does nothing.
• Remove the hard-coded Account Info settings. This adds stuff to the page template that is all duplicate functionality to the site info block and user menu blocks provided by core.

Remaining tasks/Issues to solve

• Write patch
• Test that this doesn't break existing sub-themes or hinder continued theme development.