Rollup merge of #135179 - compiler-errors:arbitrary-self-types-object, r=BoxyUwU

Make sure to use `Receiver` trait when extracting object method candidate

In method confirmation, the `extract_existential_trait_ref` function re-extracts the object type by derefing until it reaches an object. If we're assembling methods via the `Receiver` trait, make sure we re-do our work also using the receiver trait.

Fixes #135155

cc ``@adetaylor``

Author: matthiaskrgr