Fix encoder vs output shutdown crash

[aleksandr-voitenko]

Description

This PR reduces shutdown-time crashes in obs-studio-node by making shutdown wait for all active outputs to fully stop before cleanup continues. The change is made in nodeobs_service.cpp and is intended to avoid races where streaming/recording resources are destroyed while OBS output threads are still active.

The stack trace from Sentry. See, for example an issue with ID 2a0f8364

w32-pthreads +0x05277   pthread_mutex_unlock (pthread_mutex_unlock.c:61)
KERNELBASE   +0xc37ea   ResetEvent
obs          +0x6439d   gpu_encode_thread (obs-video-gpu-encode.c:126)

The stack trace is not really meaningful, but logs associated with the issue are the real source of insight.

What changed

• Improved stopStreaming(...) to handle nullptr outputs safely and to treat connecting as a busy state instead of assuming only active/reconnecting matter.
• Added shutdown helpers that detect whether an output is still busy and block shutdown until all relevant outputs have stopped.
• Updated stopAllOutputs() to:
  • wait for any prior release worker to finish,
  • stop stream outputs gracefully,
  • stop replay buffer, recording, and virtual camera outputs if still busy,
  • wait until all outputs are no longer active/connecting/reconnecting,

How Has This Been Tested?

Manually, Windows only.

Types of changes

• Bug fix (non-breaking change which fixes an issue)