Objective

• Fix a soundness issue in RawHandleWrapper::set_display_handle.
• set_display_handle is currently a safe function even though its documentation requires the provided RawDisplayHandle to be valid.
• Safe Rust can construct a RawDisplayHandle containing a non-null but invalid platform pointer and pass it to this method. Bevy may later use that value with DisplayHandle::borrow_raw or wgpu::Instance::create_surface_unsafe, both of which rely on the raw display handle being valid.
• This allows safe code to violate an invariant relied upon by unsafe code.
• This also makes set_display_handle inconsistent with set_window_handle, which already enforces the equivalent requirement through an unsafe function.

Solution

I take the minimal fix:

• Mark RawHandleWrapper::set_display_handle as unsafe.

Testing

I didn't check any test about this PR because I can't find any place that use set_display_handle. So I think this change no need to do any test.