Auto merge of #115467 - compiler-errors:assoc-ty-object-safety, r=oli…

…-obk

Do not require associated types with Self: Sized to uphold bounds when confirming object candidate

RPITITs and associated types that have `Self: Sized` bounds are opted out of the `dyn Trait` well-formedness check that happens during confirmation. This ensures that we can actually *use* `dyn Trait`s that have associated types that, e.g., have GATs and RPITITs and other naughty things as long as those are opted-out of object safety via a `Self: Sized` bound.

Fixes #115464

This seems like a natural part of rust-lang/rust#112319 (comment), and I don't think needs re-litigation.

r? `@oli-obk`