Throttle decoded frames and add log - verified, stable

[kjyoun]

This commit introduces a throttling mechanism to limit the number of video frames being decoded simultaneously. This is intended to prevent excessive memory usage and crashes, particularly during high-resolution (e.g., 8K) video playback.

The main changes include:

• A hard limit (kMaxFramesInDecoder) is introduced to cap the number of video frames that can be in the decoder pipeline at any given time.
• The CanAcceptMoreData() logic in the video renderer is updated to enforce this new limit, effectively pausing input when the decoder is at capacity.
• Adds extensive logging and frame counting to monitor the number of alive, pending, and decoded frames, which helps in debugging and verifying the throttling mechanism.