Upgrade GStreamer and Python
We should port to Python 3 and GStreamer 1.0 before O4.
They come with a few advantages:
- It will allow us to conform with IGWN conda distributions, greatly simplifying our build environment.
- Python 3 will allow better integration with PAstro
- We can take advantage of numerous Python 3 modules.
- There are better tools in GStreamer 1.0 for CPU/GPU memory management