Rename scrcpy threads

Prefix the name of threads by "scrcpy-". This improves readability in
the output of `top -H` for example.

Limit the thread names to 16 bytes, because it is limited on some
platforms.

app/src/util/process.c

@@ -64,7 +64,7 @@ sc_process_observer_init(struct sc_process_observer *observer, sc_pid pid,
     observer->listener_userdata = listener_userdata;
     observer->terminated = false;
 
-    ok = sc_thread_create(&observer->thread, run_observer, "process_observer",
+    ok = sc_thread_create(&observer->thread, run_observer, "scrcpy-proc",
                           observer);
     if (!ok) {
         sc_cond_destroy(&observer->cond_terminated);