v4l2,scripting: Add more thread names

This sets some thread names for the scripting backend's defer thread and
the v4l2 udev thread.

deps/obs-scripting/obs-scripting.c

@@ -85,6 +85,7 @@ struct defer_call {
 static void *defer_thread(void *unused)
 {
 	UNUSED_PARAMETER(unused);
+	os_set_thread_name("scripting: defer");
 
 	while (os_sem_wait(defer_call_semaphore) == 0) {
 		struct defer_call info;

plugins/linux-v4l2/v4l2-udev.c

@@ -115,6 +115,7 @@ static void *udev_event_thread(void *vptr)
 	struct udev_device *dev;
 
 	/* set up udev monitoring */
+	os_set_thread_name("v4l2: udev");
 	udev = udev_new();
 	mon = udev_monitor_new_from_netlink(udev, "udev");
 	udev_monitor_filter_add_match_subsystem_devtype(mon, "video4linux",