Better numpy v2 compatibility

[pp-mo]

#84 is a placeholder
But there are wider considerations of what dtypes we are testing / supporting.
This will also get a mention in documentation #77

This is also an opportunity to reconsider how we are sifting the available dtypes that we test against
Again, see code in #84
That is maybe a bit clunky, perhaps it would be better to include all dtypes with the appropriate dtype.kind, or something