Create dedicated message structures for FROST messages (#140)

* Create message types for FROST key gen

Taking in reader borrows absolutely wasn't feasible. Now, proper types
which can be read (and then passed directly, without a mutable borrow)
exist for key_gen. sign coming next.

* Move FROST signing to messages, not Readers/Writers/Vec<u8>

Also takes the nonce handling code and makes a dedicated file for it, 
aiming to resolve complex types and make the code more legible by 
replacing its previously inlined state.

* clippy

* Update FROST tests

* read_signature_share

* Update the Monero library to the new FROST packages

* Update processor to latest FROST

* Tweaks to terminology and documentation

crypto/frost/src/tests/literal/ed448.rs

@@ -1,5 +1,3 @@
-use std::io::Cursor;
-
 use rand_core::OsRng;
 
 use crate::{
@@ -13,32 +11,31 @@ fn ed448_8032_vector() {
   let context = hex::decode("666f6f").unwrap();
 
   #[allow(non_snake_case)]
-  let A = Ed448::read_G(&mut Cursor::new(
-    hex::decode(
+  let A = Ed448::read_G::<&[u8]>(
+    &mut hex::decode(
       "43ba28f430cdff456ae531545f7ecd0ac834a55d9358c0372bfa0c6c".to_owned() +
         "6798c0866aea01eb00742802b8438ea4cb82169c235160627b4c3a94" +
         "80",
     )
-    .unwrap(),
-  ))
+    .unwrap()
+    .as_ref(),
+  )
   .unwrap();
 
   let msg = hex::decode("03").unwrap();
 
-  let mut sig = Cursor::new(
-    hex::decode(
-      "d4f8f6131770dd46f40867d6fd5d5055de43541f8c5e35abbcd001b3".to_owned() +
-        "2a89f7d2151f7647f11d8ca2ae279fb842d607217fce6e042f6815ea" +
-        "00" +
-        "0c85741de5c8da1144a6a1aba7f96de42505d7a7298524fda538fccb" +
-        "bb754f578c1cad10d54d0d5428407e85dcbc98a49155c13764e66c3c" +
-        "00",
-    )
-    .unwrap(),
-  );
+  let sig = hex::decode(
+    "d4f8f6131770dd46f40867d6fd5d5055de43541f8c5e35abbcd001b3".to_owned() +
+      "2a89f7d2151f7647f11d8ca2ae279fb842d607217fce6e042f6815ea" +
+      "00" +
+      "0c85741de5c8da1144a6a1aba7f96de42505d7a7298524fda538fccb" +
+      "bb754f578c1cad10d54d0d5428407e85dcbc98a49155c13764e66c3c" +
+      "00",
+  )
+  .unwrap();
   #[allow(non_snake_case)]
-  let R = Ed448::read_G(&mut sig).unwrap();
-  let s = Ed448::read_F(&mut sig).unwrap();
+  let R = Ed448::read_G::<&[u8]>(&mut sig.as_ref()).unwrap();
+  let s = Ed448::read_F::<&[u8]>(&mut &sig[57 ..]).unwrap();
 
   assert!(verify(
     A,