Channel Example: Sliding Window

[hunhoffe]

This is an example of accessing sliding windows of data with channel operations. This example is rudimentary and not ideal because all data must be read in at once. A better example would allow more of a data streaming mechanism, but I'm not sure how best to do that with the current channel API. I think to do this properly you would need some sort of peek() mechanism.

If I don't have the peek() mechanism, if the sliding window is in an scf.for, I believe the only options are to put nested if/else (which I haven't yet ever used, but should be in mlir-python-extras) statements or an scf.index_switch (which is not in mlir-python-extras) with one statement per unique window in the loop... which is not a scalable way to write this sort of code.

I made this example along the way towards working on a large example, and I thought it was a useful building block, so that is why I am adding it to the programming examples (even with the sub-optimal implementation). I'm very open to suggestions for how to make it better!