Support Anoma sign / verify APIs

[paulcadman]

Verify

Anoma application logic functions will need to verify signatures. See the kudos example:

https://github.com/anoma/kudos-snippets/blob/fe8b83f288124eaf58902a566353ff3dde06beb6/docs/resource_logic.md?plain=1#L64

verification is used to check that resources have the ownership as specified in the transaction.

We're waiting for the Anoma stdlib verify call to be specified but my guess is that we'll need the following:

builtin anoma-verify
--- first argument is signed data, second argument is a public key
axiom anomaVerify : Nat -> Nat -> Bool

With example usage:

verifyLogic (r : Resource) (tx : Transaction) : Bool :=
  all (\ { n := anomaVerify n (Resource.npk r) }) (Transaction.nullifiers tx);

Sign

Signing is required to construct nullifiers in a resource. Possibly only for tests?

https://github.com/anoma/anoma/blob/1522993620fff4a9a998379a49f3d7a51e7a01d5/test/resource_test.exs#L135

https://github.com/anoma/anoma/blob/base/lib/anoma/resource.ex#L59

Proposed builtin:

builtin anoma-sign
--- first argument is the data to sign, second argument is a private key
axiom anomaSign : {A : Type} -> A -> Nat -> Bool

The implementation should use the Nockma/Anoma serialisation to serialise the data to sign before calling the Anoma stdlib sign function.

[paulcadman]

Completed by #2798