Auto merge of #108095 - soc:drop-contains, r=Amanieu

Drop unstable `Option::contains`, `Result::contains`, `Result::contains_err`

This is a proposal to drop the three functions `Option::contains`, `Result::contains` and `Result::contains_err`.

The discovery of `Option::is_some_with`/`Result::is_ok_with`/`Result::is_err_with` in rust-lang/rust#93051 obviates the need for these methods (non-stabilization tracked in rust-lang/rust#62358).

An additional benefit of change is that it avoids spurious error messages in IDEs, when `contains` is supplied by a third-party library:
![option-result-unstable](https://user-images.githubusercontent.com/42493/219127961-13cb559e-6ee8-4449-8dc9-d28d07270ad5.png)

Author: bors