Add `_≮_` and `_≰_` to bundles in the binary relation hierarchy.

[mechvel]

In lib-1.3 I see _≉_ in Setoid,
but I do not find ≰, ≮
(I expect they to be defined via ¬_).
I grepped for it in Relation.Binary, Relation.Binary.Construct, and do not find it.
Probably it needs to be in Preorder or in PartialOrder.
?

[MatthewDaggitt]

I'm not sure we have a good symbol for the negation of the order for ~. I'd therefore probably add _≰_ to PartialOrder and _≮_ to StrictPartialOrder for now.

[MatthewDaggitt]

There is now a good symbol for \~n for negated tilde.

[jamesmckinna]

Any (potential) interaction with any candidate solution to issue #1635?

[MatthewDaggitt]

Hmm yes. The precedence of the candidate solution should be < 4 otherwise it will interfere with both this and the non-negated equality.

[jamesmckinna]

Now that we have closed #1635, would precedence level = 4 suffice?
Currently each of _≈_ , _≉_ , and _∼_ are declared at level 4...

[jamesmckinna]

Oh, but this has turned out to be more complicated than I first realised...
... and immediately gives rise to the linked issue #2096... and hence (the need/desire for) further refactoring in the same spirit #2098 to introduced notation systematically for the flipped relations... see #2099 for an opening bid on that.