Rollup merge of #95603 - compiler-errors:dyn-return, r=oli-obk

Fix late-bound ICE in `dyn` return type suggestion

This fixes the root-cause of the attached issues -- the root problem is that we're using the return type from a signature with late-bound instead of early-bound regions. The change on line 1087 (`let Some(liberated_sig) = typeck_results.liberated_fn_sigs().get(fn_hir_id) else { return false; };`) makes sure we're grabbing the _right_ return type for this suggestion to check the `dyn` predicates with.

Fixes #91801
Fixes #91803

This fix also includes some drive-by changes, specifically:

1. Don't suggest boxing when we have `-> dyn Trait` and are already returning `Box<T>` where `T: Trait` (before we always boxed the value).
2. Suggestion applies even when the return type is a type alias (e.g. `type Foo = dyn Trait`). This does cause the suggestion to expand to the aliased type, but I think it's still beneficial.
3. Split up the multipart suggestion because there's a 6-line max in the printed output...

I am open to splitting out the above changes, if we just want to fix the ICE first.

cc: ```@terrarier2111``` and #92289

0 files changed, 0 insertions, 0 deletions