Auto merge of #156224 - khyperia:unnormalized-migration, r=BoxyUwU

Unnormalized migration: assert_fully_normalized, struct_tail, and `field.ty`



tracking issue: https://github.com/rust-lang/rust/issues/155345 (first checkbox, and partial second checkbox, of that issue)

I'm going a bit slower than expected (less free time than I'd hope, lots of GCA work that I'm doing instead), and figured I'd just submit what I have now rather than building up a big batch of changes. Slow and steady!

r? @lcnr