nightly features (AFIT etc.)

[fasterthanlime]

List of features we used, and are they stabilized:

• 😎 AFIT (async fn in trait)
  • Stabilize async fn and return-position impl Trait in trait rust-lang/rust#115822
• 😎 RPITIT (return position impl trait in trait)
  • Stabilize async fn and return-position impl Trait in trait rust-lang/rust#115822
• ☀️ TAIT (type alias impl trait)
  • Tracking issue for RFC 2515, "Permit impl Trait in type aliases" rust-lang/rust#63063
• 😶 impl_trait_in_assoc_type:
  • Tracking issue for RFC 2515, "Permit impl Trait in type aliases" rust-lang/rust#63063
  • (was part of TAIT, then split off to stabilize "min TAIT" first?)
• ❄️ thread_local
  • Tracking issue for thread_local stabilization rust-lang/rust#29594

[fasterthanlime]

I've decided to stop waiting for the remaining async features and switch fluke to stable.. today!

There might be a small perf drop due to switching from the thread_local attr to the macro, but I'm okay with it - I want to switch to io_uring "provided buffers" afterwards anyway.