This PR adds basic lemmas about `Ordering`, describing the interaction
of `isLT`/`isLE`/`isGE`/`isGT`, `swap` and the constructors.
Additionally, it refactors the instance derivation code such that a
`LawfulBEq Ordering` instance is also derived automatically.
Some of these lemmas are helpful for the `TreeMap` verification.
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Co-authored-by: Paul Reichert <6992158+datokrat@users.noreply.github.com>
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