Rollup merge of #148228 - clarfonthey:regression-next-solver, r=nnethercote

Run regression test for #147964 on next solver too Original regression: #147964 Longer-term tracking of issue: #148028 For now, this just makes sure that whatever tests we keep are working the same under both the current solver and the next solver, until we decide what to do with them.

Author: matthiaskrgr

tests/ui/traits/generic-cow-inference-regression.rs

@@ -1,3 +1,5 @@
+//@[new] compile-flags: -Znext-solver
+//@ revisions: old new
 //@ run-pass
 
 // regression test for #147964: