BQ expression fixes (#17347)

This was a miserable grind in the old BQ syntax but a happy fun time in the new BQ syntax, basically just turning it on and squashing a bunch of test bugs.

One test bug to note especially is that the underscore-transformed set of bird scarcity data for the bird scarcity tests is actually necessary, because BQ will hit you with a complaint about underscores even if you successfully and correctly quote the table names.