fix: consistent byteorder settings

[ikrommyd]

Making a few changes to have consistent byteorder settings in the codebase.

First of all, ak.to_buffers defaults to native byteorder here:

awkward/src/awkward/operations/ak_to_buffers.py

Line 24 in 8640184

byteorder=ak._util.native_byteorder,

We do the same for ak._do.to_buffers (which is used inside ak.to_buffers) for consistency even though it's semi-public API.

Secondly, buffers are generally native (always or almost always) as they are in-memory. Therefore ak.to_buffers should have the same defaults as ak.to_buffers. ak.from_buffers(*ak.to_buffers(...)) should just work on all systems. One shouldn't have to specify ak.from_buffers(*ak.to_buffers(...), byteorder=ak._util.native_byteorder) in order for this to work on a big-endian system for example.

And finally, awkward expects arrays/dtypes to be in native byteorder when the NumpyArray and Index classes are constructed as wrappers around the buffers. We modify the naming in the tests to express just that as the default in awkward internally is not "little". It's "native".

All of these changes are no-ops for little endian systems as ak._util.native_byteorder is "<". But they make byteorder settings more self-consistent in the codebase and make these ops that depend on byteorder seamless in big endian systems without one having to specify byteorder=">" explicitly just because they are on a different system.

[github-actions]

The documentation preview is ready to be viewed at http://preview.awkward-array.org.s3-website.us-east-1.amazonaws.com/PR3954

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.25%. Comparing base (8640184) to head (2594039).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

Files with missing lines	Coverage Δ
src/awkward/_do.py	84.70% <ø> (ø)
src/awkward/operations/ak_from_buffers.py	94.44% <ø> (ø)

... and 9 files with indirect coverage changes

[ariostas]

Looks good to me. Thank you, @ikrommyd!