Bindgen: accept closure directly in event registration methods

[Copilot]

Follow-up to #4435: under --minimal, event registration methods now take the handler closure directly and construct the delegate internally, so the delegate type can be inferred.

Before:

let routed = Xaml::RoutedEventHandler::new(move |_sender, _args| Ok(()));
let revoker = source.Click(&routed)?;

After:

let revoker = source.Click(move |_sender, _args| Ok(()))?;

Changes

• crates/libs/bindgen/src/types/method.rs — In the is_event_add branch, detect the Type::Delegate parameter and replace its P{n}: Param<Delegate> generic with F: Fn(<delegate Invoke sig>) -> Result<()> + Send + 'static (reusing Delegate::method().write_impl_signature so the bound matches Delegate::new's constraint exactly). The body prepends let handler = <Delegate>::new(handler); (UFCS wrapper handles generic delegates like TypedEventHandler<T, U>) and passes Interface::as_raw(&handler) to the vtable call. Non-delegate parameters keep their existing convertible / IReference handling. Falls back to the previous signature if no delegate parameter is found.
• crates/tests/libs/bindgen/data/bindgen/auto_events/expected.rs — Regenerated by the fixture.
• crates/tests/winrt/events_client/src/auto_bindings.rs — Regenerated via the crate's build.rs.
• crates/tests/winrt/events_client/src/lib.rs — Auto-events test fixture from Add non-generic EventRevoker + --minimal bindgen event-revoker support #4435 updated to the closure-only syntax.