[nll] unresolved inference variable in outlives: _#3t

[nikomatsakis]

The latest crater run reported some ICE errors that look very similar to #52057 (but are potentially different). This crate is small but pretty involved with its wrappers over hyper, tokio, and futures, resulting in a lot of associated types and bounds, and some of those 'static bounds might have a weird interaction with the NLL typeck, impl Trait, and maybe delay_span_bug.

@lqd minimized it to only one such error, but note that the real code has 5 or 6 of them, so it would be good to verify any potential fix on the hyper-stub crate itself rather than just this minimized repro. Playground.

List of crate failures

• hyper-stub-0.1.0: log
• dekellum.body-image.11424ec2c7d4363c5f5f1cf6eb1e2d3fec7dc2ec: log

[nikomatsakis]

Fix in #53580