Move `sliding_window_view` to the main module and add `step_size`

1. Writing np.lib.stride_tricks.sliding_window_view is a bit of a mouthful, I think it would be better if it was placed inside the main module. (also doing import from is a bit inconvenient)
2. I suggest adding a step_size parameter to the function, an example of its use would be:

x = np.arange(10)
sliding_window_view(x, 3, step_size=2) 

>> array([[0, 1, 2],
          [2, 3, 4],
          [4, 5, 6],
          [6, 7, 8]])

[eric-wieser]

I argued against step_size when we designed this function, because you can get that behavior already with sliding_window_view(x, 3)[::2].

[rgommers]

Hi @rgommers, I’m curious to know if there has been any development regarding the mentioned reorganization?

gh-18447 made some initial steps, but it seems to have stalled.

if possible I would suggest renaming it to window.

That’s way too generic a name; even in numpy itself we have other “window functions” like bartlett, hanning, etc.