Bind epoll_loop to last online CPU

[li041]

• Currently, the epoll_loop is created without CPU affinity, which
  can result in it being scheduled on CPU0. Since CPU0 is often handling
  interrupts and other critical system tasks (zone0), this can interfere
  with system responsiveness.

• This PR changes the initialize_event_monitor to bind epoll_loop to
  the last online CPU available to the process. The thread affinity is
  set using pthread_setaffinity_np after determining the last CPU from
  sched_getaffinity.

[Copilot]

Pull request overview

This PR adds CPU affinity binding for the epoll_loop thread to prevent it from being scheduled on CPU0, which typically handles interrupts and critical system tasks. The implementation determines the last available CPU using sched_getaffinity and binds the event monitor thread to that CPU using pthread_setaffinity_np.

Changes:

• Added _GNU_SOURCE definition and sched.h include for CPU affinity functions
• Implemented CPU affinity logic in initialize_event_monitor to bind the epoll_loop thread to the last online CPU
• Added logging for CPU affinity operations (success and failure cases)

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[agicy]

Looks good to me.