feat: add recursive argument to expected_from_buffers

[agoose77]

In the work to support buffer-shape touching in dask-awkward, I found it useful to be able to disable recursion in expected_from_buffers in order to identify the buffers associated directly with each form node. I think this has merit, so I've created this PR.

[codecov]

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Additional details and impacted files

Files	Coverage Δ
src/awkward/forms/bitmaskedform.py	83.92% <100.00%> (+0.14%)	⬆️
src/awkward/forms/bytemaskedform.py	85.84% <100.00%> (+0.13%)	⬆️
src/awkward/forms/emptyform.py	86.86% <ø> (ø)
src/awkward/forms/form.py	82.12% <100.00%> (ø)
src/awkward/forms/indexedform.py	80.17% <100.00%> (+0.17%)	⬆️
src/awkward/forms/indexedoptionform.py	89.71% <100.00%> (+0.09%)	⬆️
src/awkward/forms/listform.py	79.13% <100.00%> (+0.18%)	⬆️
src/awkward/forms/listoffsetform.py	94.33% <100.00%> (+0.05%)	⬆️
src/awkward/forms/numpyform.py	83.72% <ø> (ø)
src/awkward/forms/recordform.py	90.55% <100.00%> (+0.05%)	⬆️
... and 3 more

[jpivarski]

I don't see any examples in this PR in which the new recursive argument gets used, but in principle it could be useful to have.

The default should be recursive=True, as you have it here, since its primary use-case is to find out what the containers needs to have, and that's a question for a whole tree, not a single node.

[agoose77]

I don't see any examples in this PR in which the new recursive argument gets used, but in principle it could be useful to have.

The test file uses both variations :)