Likes: Add ability to discover which posts have the most likes

### Impacted plugin

Jetpack

### What

Add ability to discover which posts have the most likes

### How

This could be done in the posts lists page. In wp-admin, there are sorting columns, and a likes column, but the likes column cannot be sorted.

Or, we could add it to the stats page. We have a tab that says Likes, and we have top posts and pages reports. Perhaps we could add one for top liked posts?

If we wanted to get extra fancy, we could allow folks to show most liked posts in a blog posts block. But I think letting the admin easily see for themselves which posts have the most likes is a good start!

Requested here:
https://wordpress.com/forums/topic/can-you-sort-posts-by-likes/

Start with the wp-admin posts list's existing likes column and the Stats page's Likes tab, including the top posts and pages reports. Clarify which entry point should expose the result, then trace its existing data and UI flow; done means administrators can reliably identify their most-liked posts through the chosen interface, with coverage for the new behavior.

Written by the indexing model from the issue text.