Refactor crypto-related traits implementations in term of Public/Signature Bytes (#3806)

Another simple refactory to prune some duplicate code

Follow up of: https://github.com/paritytech/polkadot-sdk/pull/3684

substrate/primitives/application-crypto/src/lib.rs

@@ -26,7 +26,7 @@ pub use sp_core::crypto::{DeriveError, Pair, SecretStringError};
 #[doc(hidden)]
 pub use sp_core::{
 	self,
-	crypto::{ByteArray, CryptoType, Derive, IsWrappedBy, Public, UncheckedFrom, Wraps},
+	crypto::{ByteArray, CryptoType, Derive, IsWrappedBy, Public, Signature, UncheckedFrom, Wraps},
 	RuntimeDebug,
 };
 
@@ -505,6 +505,12 @@ macro_rules! app_crypto_signature_common {
 			}
 		}
 
+		impl AsMut<[u8]> for Signature {
+			fn as_mut(&mut self) -> &mut [u8] {
+				self.0.as_mut()
+			}
+		}
+
 		impl $crate::AppSignature for Signature {
 			type Generic = $sig;
 		}
@@ -525,6 +531,12 @@ macro_rules! app_crypto_signature_common {
 			}
 		}
 
+		impl $crate::Signature for Signature {}
+
+		impl $crate::ByteArray for Signature {
+			const LEN: usize = <$sig>::LEN;
+		}
+
 		impl Signature {
 			/// Convert into wrapped generic signature type.
 			pub fn into_inner(self) -> $sig {