[ refactor ] rationalise the common APIs for List and Vec versions of Data.*.Relation.Binary.Lex.*

[jamesmckinna]

I started thinking about this with #2679 and then #2682 / #2683 ...

But this PR is really more about trying to identify a 'common' API for the lexicographic ordering(s) on Vec and List, and with that, the emphasis seems more to be about the 'atomic' properties such as Symmetric etc.

Originally posted by @jamesmckinna in #2679

Now, the APIs are not exactly the same (cf. the comments on #2682 re: WellFounded), but there is enough in common that I think this is worthwhile doing, even if it isn't entirely obvious that there is an actual DRY gain, merely one of 'cognate duplication'.