Out of proc languages stream support

For all Node.js bindings (trigger/input/output) streaming is not supported - the data is put into an in memory buffer first. This can cause out of memory issues for people attempting to process large blobs for example.

We should investigate ways to support a streaming model, as you can optionally do in C# (by binding to a Stream). E.g. we might have a binding hint that allows the function to request a stream, and we provide the user code with a stream over the underlying SDK stream.

Note that if we move out of process for languages, streaming is complicated. We need to consider this when making any new programming model decisions.

The issue mentions Node.js trigger, input, and output bindings, plus C# Stream binding as a comparison; start by mapping how these bindings currently buffer data for out-of-process languages. Done means defining and implementing a viable streaming model for large blobs while accounting for its impact on future programming-model decisions.

Written by the indexing model from the issue text.