optimization: Speed up image saving procedure

[hilookas]

What this does

PIL save require time consuming image encoding, which is slow, and cause image queue backing up and make a OOM when doing a realtime teleoprate.

With pyav, we can make is much faster and less resource usage.

How it was tested

TODO benchmarking

How to checkout & try? (for the reviewer)

Close https://github.com/huggingface/lerobot/issues/360