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.
Event, input source, error, data transfer, native key, IME request,
scroll delta and fullscreen enums can now gain variants without a
breaking change. Backends and examples get wildcard arms where they
matched exhaustively; unknown IME requests are reported as
ImeRequestError::NotSupported and unknown fullscreen modes behave
like Fullscreen::Borderless(None).
