Auto merge of #116435 - compiler-errors:re-erased, r=lcnr

Handle `ReErased` in responses in new solver

There are legitimate cases in the compiler where we return `ReErased` for lifetimes that are uncaptured in the hidden type of an opaque. For example, in the test committed below, we ignore ignore the bivariant lifetimes of an opaque when it's inferred as the hidden type of another opaque. This may result in a `type_of(Opaque)` call returning a type that references `ReErased`. Let's handle this gracefully in the new solver.

Also added a `rustc_hidden_type_of_opaques` attr to print hidden types. This seems useful for opaques.

r? lcnr

Author: bors