units: Audit all types for correct usage of Ord vs ArbitraryOrd

[tcharding]

Not all types have an order but putting types into struct that require Ord is common, this is what we wrote the ordered crate for.

Audit all the types in units and check that they correctly either derive Ord and PartialOrd or implement ArbitraryOrd.

[15IITian]

I'll take this up

[tcharding]

Oh woops, I should have mentioned originally but I was thinking of after #2569 lands - there is currently only the amount types in units. My bad.

[15IITian]

there is currently only the amount types in units.

Yeah , I was pretty confused initially -> but now I see there are other types too which are related to amounts so can check them until #2569 got merge.

[15IITian]

Recently I checked after merging of #2569 and IMO , Everything looks fine .