New Native Operation PublicKeyOf (#355)

* wrote some initial code

* added way to input private key into circuit

* TypedValue::SecretKey hashed as 10 32-bit limbs

* Check PublicKeyOf in Frontend and Middleware

* Diff review

* PR review

* Finish utest

* Fix bounds check

* added giving secret key witness to circuit

* Test & doc improvements

* added private key comparison to circuit and added test cases

* cargo fmt

* Add frontend tests for PublicKeyOf

* Add public_key_of and hash_of to op! macro

* Add ownership check to ticket example

* Group order checking in tests

* More negative test cases at circuit level

* Cleanups after self review

* clippy fixes

* Fixes after merge.  Temporarily remove plonky2 commit hash

* Add a nullifier to the ticket test example

* Test PublicKeyOf with a real prover (not mock)

* plonky-u32 dependency

* feat: optimize operation checks

Skip the circuits that verify operation checks other than None, Copy or
NewEntry for the public statements.  This works because public
statements are created by copying private statements, so we never use
the other operation checks in those slots.

---------

Co-authored-by: Andrew Twyman <artwyman@gmail.com>
Co-authored-by: Eduard S. <eduardsanou@posteo.net>

src/backends/plonky2/mainpod/statement.rs

@@ -70,6 +70,10 @@ impl TryFrom<Statement> for middleware::Statement {
                 (NP::MaxOf, &[a1, a2, a3]) => {
                     S::MaxOf(a1.try_into()?, a2.try_into()?, a3.try_into()?)
                 }
+                (NP::HashOf, &[a1, a2, a3]) => {
+                    S::HashOf(a1.try_into()?, a2.try_into()?, a3.try_into()?)
+                }
+                (NP::PublicKeyOf, &[a1, a2]) => S::PublicKeyOf(a1.try_into()?, a2.try_into()?),
                 _ => Err(Error::custom(format!(
                     "Ill-formed statement expression {:?}",
                     s