[23.2] Npz sniffing: do not read the whole file

[bernt-matthias]

Backport of #17672

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[github-actions]

This PR was merged without a "kind/" label, please correct.

[nsoranzo]

@bernt-matthias This (as well as #17672 ) broke some integration tests, can you check please?

[mvdbeek]

I think I found a nice way to fix the sniffer by checking if any zipped file is a .npy file in #17679

[bernt-matthias]

Hrm. Seems that npz files are just zip files .. contrary to the docs the only property that distinguishes them from zip files numpy/numpy#26004 is not enforced.

I could implement this test, i.e. get a file listing from the zip and check if all are .npy. Otherwise I would suggest to drop the sniffer.

[mvdbeek]

That's what #17679 does

[mvdbeek]

except it's valid for some files not to be .npy files, so I'm using any() ... I don't think we care since sniffing doesn't have to be perect