Slap better content into the UI block from #51377.

cc @Strum355 - this could be a good area to start on simply extracting and formatting (in plain text) the current status of a migration (where did we come from, where are we going, how far are we, what migrations need to be applied, what oobmigrations need to be applied, any errors, etc). We'll end up slapping it in a UI somewhere, but updating the upgradestore (or wherever we end up implementing it) to understand the correct progress and state of the upgrade is going to be the fun part.