Autofix/migration suggestion

I remember at some point y'all were asking what would some good migrations be. Well, here's one! An autofix that adds a variable to all of the queries it's part of, perhaps with a specific default value as well

Start by locating the query migration and autofix entry points, then read how existing migrations are specified and tested. Define the intended variable insertion and default-value behavior before implementing it; done means the proposed migration applies consistently to every relevant query and has coverage for its behavior.

Written by the indexing model from the issue text.