make vector cmp match axes

[adienes]

closes #48916 as suggested by @oscardssmith

I believe the more consistent behavior here would be for isless to error when comparing two Arrays a and b where eachindex(a,b)∉(eachindex(a), eachindex(b)) (similarly to how it works with Complex numbers or other collections like Dict that don't have an ordering.

[adienes]

very tangential, but it's a shame to have to use exceptions here. partial orders seem like the perfect use case for a Some-or-nothing API

[adienes]

@nanosoldier runtests()