Better compile test, fixup abstract methods

[scotts]

This PR does three things:

1. Removes a torch.compile test from ops that used a very basic version of what would eventually become VideoDecoder in Python. Also removes that basic class.
2. Implements a new test using the actual VideoDecoder. We get a graph break, which we can avoid by setting a flag. I think it's worth keeping this test around for now to know if we get more. I think this will eventually become a priority.
3. The compilation test revealed that we missed removing stream_index from our abstraction functions when we removed them from the API implementations.