core: Remove hitch tracking. Hasn't been an active problem, and the traces are sufficient to diagnose.

src/ssb.h

@@ -1006,15 +1006,6 @@ void tf_ssb_record_thread_busy(tf_ssb_t* ssb, bool busy);
 */
 float tf_ssb_get_average_thread_percent(tf_ssb_t* ssb);
 
-/**
-** Register a callback to be called when the main thread blocks for an
-** unreasonable amount of time.
-** @param ssb The SSB instance.
-** @param callback The callback to call.
-** @param user_data User data to pass to the callback.
-*/
-void tf_ssb_set_hitch_callback(tf_ssb_t* ssb, void (*callback)(const char* name, uint64_t duration_ns, void* user_data), void* user_data);
-
 /**
 ** Get the queue of messages in the progress of being stored.
 ** @param ssb The SSB instance.