Auto merge of #103308 - sunfishcode:sunfishcode/wasi-io-safety, r=joshtriplett

Mark `std::os::wasi::io::AsFd` etc. as stable.

io_safety was stabilized in Rust 1.63, so mark the io_safety exports in `std::os::wasi::io` as stable.

Fixes #103306.

library/std/src/os/wasi/io/mod.rs

 //! WASI-specific extensions to general I/O primitives.
 
-#![unstable(feature = "wasi_ext", issue = "71213")]
+#![stable(feature = "io_safety", since = "1.63.0")]
 
-#[unstable(feature = "wasi_ext", issue = "71213")]
+#[stable(feature = "io_safety", since = "1.63.0")]
 pub use crate::os::fd::*;