Auto merge of #15152 - alibektas:14987, r=Veykril,lowr

assist : generate trait from impl

fixes #14987 . As the name suggests this assist is used to generate traits from inherent impls while adapting the original impl to fit to the newly generated trait. I made some decisions regarding when the assist should be applicable. These are surely open to discussion. I looking forward to any feedback.

![generate_trait_from_impl_v1](https://github.com/rust-lang/rust-analyzer/assets/20956650/05d4dda5-604a-4108-8b82-9b60bd45894a)

Author: bors