Rollup merge of #119715 - Nadrieril:graceful-type-error, r=compiler-errors

Exhaustiveness: abort on type error

This adds an error path to exhaustiveness checking so that we abort instead of ICEing when encountering a stray `ty::Error`.

Fixes rust-lang/rust#119493
Fixes rust-lang/rust#119778

r? `@compiler-errors`

Author: matthiaskrgr