`clippy::return_self_not_must_use` is overreaching

Using 1.59.0-beta.3, the following illustrates the point:

warning: missing `#[must_use]` attribute on a method returning `Self`
  --> libp2p-streaming-response/src/v2/behaviour.rs:32:5
   |
32 | /     pub fn with_request_timeout(self, request_timeout: Duration) -> Self {
33 | |         Self {
34 | |             request_timeout,
35 | |             ..self
36 | |         }
37 | |     }
   | |_____^
   |
   = note: `#[warn(clippy::return_self_not_must_use)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#return_self_not_must_use

I can see how a method that takes &self and produces Self may be misused (although I don’t think that is compelling enough to warrant a default lint), but the above method is not susceptible to programmer mistakes, thanks to Rust’s affine type system. If you deem this worthy of a fix, I may try my hand at it.

Start by reproducing the warning from clippy::return_self_not_must_use with Rust 1.59.0-beta.3 using the example in libp2p-streaming-response/src/v2/behaviour.rs. Compare the lint's treatment of methods consuming self with methods taking &self; completion requires an agreed scope for the lint's behavior and corresponding Clippy coverage.