Rollup merge of #126968 - lqd:issue-126670, r=compiler-errors

Don't ICE during RPITIT refinement checking for resolution errors after normalization

#126670 shows a case where resolution errors after normalization can happen during RPITIT refinement checking. Our tests didn't reach this path before, and we explicitly ICEd until we had a test. We can now delay a bug since we're sure it is reachable and have the test from the isue.

The comment I added likely still needs more expert wordsmithing.

r? ``@compiler-errors`` who's making me work during vacation (j/k).
Fixes #126670

Author: matthiaskrgr