construct properties always trigger the deprecated property warning

To reproduce:

G_DEBUG=fatal-warnings G_ENABLE_DIAGNOSTIC=1 gdb --args gio info file:///

for which the important part is that GDBus calls into g_socket_client_new() which constructs a GSocketClient with default properties:

g_object_new (G_TYPE_SOCKET_CLIENT, NULL);

Expected result: no warning, because the deprecated GSocketClient:tls-validation-flags property was correctly not specified

Actual result:

(gio info:244202): GLib-GObject-WARNING **: 09:57:15.537: The property GSocketClient:tls-validation-flags
is deprecated and shouldn't be used anymore. It will be removed in a future version.

(followed by a crash because I used G_DEBUG=fatal-warnings)

From the backtrace, this appears to be because g_object_new_internal() sets all construct properties to their default values by calling object_set_property(), but object_set_property() does not have a way to know which ones were explicitly provided by the user in a GObjectConstructParam and which ones are just being set to their defaults.