[WIP] Add audio effect stream

[fire]

This is a work in progress api for review.

The goal is to get specific sized chunks from a ring buffer saving the current effect.

Use case:

Effect streams the current bus so that we get either zero or equally sized vector of floats in left / right format. This allows something like opus to have same sized buffers to use as input for voip.

godotengine/godot-proposals#399

[fire]

Closing for a better implementation.

Godot has a RingBuffer class you can check as reference, you need two of those

Your AudioEffect is fed audio and expects you to feed audio back in a single callback

The audio you are fed is pushed to the ringbuffer, and you pull from the second ringbuffer for audio to push

https://github.com/godotengine/godot/blob/a7f49ac9a107820a62677ee3fb49d38982a25165/core/ring_buffer.h

In another thread, which is updated periodically, you fill packets by reading from the first ringbuffer and send them, and you decompress packets you get and feed them to the second ringbuffer

[reduz] that said, I feel that is not a great approach for voip, since you need to account for many different situations like delays and running out of packets. I am sure there are better implementations out there

[reduz] also you need to account for packets arriving out of order and that kind of stuff