Load CODEOWNER details on demand for pages and directories

Proposal

Stop loading CODEOWNERS on the page load, instead have a link and load them only on request? (comment)

There's an opportunity to greatly reduce the load on the backend here. The query seems to be quite expensive. For example, here we are loading 133 code owners for a single file. The response weighs 5.5KB and takes almost a full second to resolve. If there's a way we avoid making this query on every file and directory in repos, we would spare a lot of resources.