special case "row.names" attribute

[moodymudskipper]

There's a weird internal thing going on to automate row names, and while identical doesn't see it, it has (rare) consequences.

https://twitter.com/antoine_fabri/status/1777636463980499038

tidyverse/tibble#1571

I don't know of a way to assess which method was used without trying 1 and comparing to the original object after serialisation. I think we don't want to do that though due to the overhead. I think the auto names should be the default in non artificial cases, it's what dput does too. So let's do that.