background Enable FIFO scheduling by default for RTDE producer thread (#536)

Improves the scheduling configuration of the thread responsible
for receiving and processing robot communication data.

When `read_packages_in_background` is enabled, the RTDE client creates a
dedicated background thread for continuously receiving RTDE data
packages.

Previously, this thread was executed using the operating system's
default scheduling policy. Under system load, scheduling delays could
introduce additional latency and timing jitter while processing incoming
RTDE data.

This PR configures the RTDE background read thread to request the
highest available FIFO scheduling priority using the existing helper
functions.

Author: srvald

src/rtde/rtde_client.cpp

@@ -30,6 +30,7 @@
 #include "ur_client_library/exceptions.h"
 #include "ur_client_library/log.h"
 #include "ur_client_library/rtde/data_package.h"
+#include "ur_client_library/helpers.h"
 #include <algorithm>
 #include <chrono>
 #include <string>
@@ -964,6 +965,10 @@ void RTDEClient::stopBackgroundRead()
 
 void RTDEClient::backgroundReadThreadFunc()
 {
+  pthread_t this_thread = pthread_self();
+  const int max_thread_priority = sched_get_priority_max(SCHED_FIFO);
+  setFiFoScheduling(this_thread, max_thread_priority);
+
   while (background_read_running_)
   {
     std::unique_lock<std::mutex> lock(reconnect_mutex_, std::defer_lock);