Fix specifying memory order in v2 arrays

[dstansby]

Fixes #2950

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.rst
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[d-v-b]

this looks good! and my explanation from #2950 was wrong -- this has nothing to do with the global config, it's just buggy code (that i think I wrote).

[dstansby]

So I updated the test, and it now passes a bit more. But the check that the actual array data is F-order now fails, so it looks like the data still isn't (and never was) actually being written in F-order. More digging needed...