Move associated types to top of struct

There is no obvious reason why the associated types for `MiniscriptKey`
are below the trait methods. Move them to the top.

Note, the diff shows moving functions not associated types - same thing.

Refactor only, no logic changes.

Author: tcharding

src/lib.rs

@@ -149,17 +149,6 @@ pub use crate::primitives::threshold::{Threshold, ThresholdError};
 
 /// Trait representing a key which can be converted to a hash type.
 pub trait MiniscriptKey: Clone + Eq + Ord + fmt::Debug + fmt::Display + hash::Hash {
-    /// Returns true if the key is serialized uncompressed.
-    fn is_uncompressed(&self) -> bool;
-
-    /// Returns true if the key is an x-only pubkey.
-    fn is_x_only_key(&self) -> bool;
-
-    /// Returns the number of different derivation paths in this key.
-    ///
-    /// Only >1 for keys in BIP389 multipath descriptors.
-    fn num_der_paths(&self) -> usize;
-
     /// The type used in the sha256 fragment.
     type Sha256: Clone + Eq + Ord + fmt::Display + fmt::Debug + hash::Hash;
 
@@ -171,6 +160,17 @@ pub trait MiniscriptKey: Clone + Eq + Ord + fmt::Debug + fmt::Display + hash::Ha
 
     /// The type used in the hash160 fragment.
     type Hash160: Clone + Eq + Ord + fmt::Display + fmt::Debug + hash::Hash;
+
+    /// Returns true if the key is serialized uncompressed.
+    fn is_uncompressed(&self) -> bool;
+
+    /// Returns true if the key is an x-only pubkey.
+    fn is_x_only_key(&self) -> bool;
+
+    /// Returns the number of different derivation paths in this key.
+    ///
+    /// Only >1 for keys in BIP389 multipath descriptors.
+    fn num_der_paths(&self) -> usize;
 }
 
 impl MiniscriptKey for bitcoin::secp256k1::PublicKey {