Remove the AsAny helper trait

Trait upcasting (rust-lang/rust#65991) is stable since Rust 1.86, which
is already the MSRV, so dyn trait objects coerce to dyn Any directly.
Traits that needed AsAny now list Any as their supertrait, and the
as_any module is renamed to casting as only the impl_dyn_casting macro
remains.

winit-core/src/lib.rs

@@ -14,7 +14,7 @@
 #![warn(clippy::exhaustive_enums)]
 
 #[macro_use]
-pub mod as_any;
+pub mod casting;
 pub mod cursor;
 #[macro_use]
 pub mod error;