std: Drop Total from Total{Eq,Ord}

This completes the last stage of the renaming of the comparison hierarchy of
traits. This change renames TotalEq to Eq and TotalOrd to Ord.

In the future the new Eq/Ord will be filled out with their appropriate methods,
but for now this change is purely a renaming change.

This continues the work of #12517, continuing the work in #14534. This patch accomplishes the final rename of `TotalEq` to `TotalOrd`. I wanted to get this patch landed ASAP so we don't have to deal much with "where did `Eq` and `Ord` go?"

I have yet to do another pruning pass over the compiler to change all usage of `PartialEq` to `Eq` where necessary. I will do this soon as well.