Adds va_marshallers to the ClutterStage signals. This allows for better
stack traces to be retrieved when profiling. Additionally, since the
generic marshaller was using GBoxedCopy/GBoxedFree functions for the
GValue usage, the previous code was acquiring a global reader/writer
lock in GObject via g_boxed_free() usage.
With G_SIGNAL_TYPE_STATIC_SCOPE, the generated marshallers can avoid
the additional copy/free on the instance.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3204>
150a9e35ad