Refactor the settings page to use `@wordpress/build` and modern WordPress packages

[retlehs]

The settings page is currently a mix of PHP-rendered templates, the WordPress Settings API, WP_List_Table, and vanilla JS, built with @10up/scripts

Proposal

Refactor the entire settings page to a React-based interface built on:

• @wordpress/build — the new official build tooling for WordPress plugins. Background: "WordPress Build: the next generation of WordPress plugin build tooling".
• @wordpress/components — for tabs, buttons, form controls, modals, notices.
• @wordpress/dataviews — to replace the WP_List_Table repository list with a modern, sortable, filterable view that supports inline actions.
• The existing ghrp/v1 REST endpoints — no backend changes needed for most of this (everything the page does already has a REST route).

[jakemgold]

Keeping this issue open for the future, but I don't think a major refactoring is needed or all that useful for a 1.0 release, especially since most of WordPress itself still doesn't use these new conventions.