Rename lemma `satisfied` to `any⇒satisfiable` in `*.Relation.Unary.Any`

[MatthewDaggitt]

See discussion in #2862 where @jamesmckinna makes this suggestion. I agree that it is a much better name.

Really the lemma that should be called satisfiable should be Satisfiable P -> Satisfiable (Any P). Of course the opposite lemma also holds Satisfiable (Any P) -> Satisfiable P so maybe the naming needs to be thought about more carefully.

[jamesmckinna]

Good to lift this out separately.
As with #2846 , the story is perhaps a bit trickier than meets the eye at first glance.