Debug v1 of sample factory

[Abc11c]

Hi @alex-petrenko,

Thank you for such a great code!

I'm working on some RL algorithms (intrinsic reward-based ones for the MiniGrid environment) based on the version here.

I was wondering if there are any tricks for debugging the code, specifically on how to synchronize the threads, similar to the current version as seen in the serial mode.

I can't get breakpoint() to work because of threading, which makes it hard to debug.

Any pointers would help. Thanks!

Best regards, Ashwath