Adds support for inspecting a hex encoded public key (#7344)

* Adds support for inspecting a hex encoded public key

This adds support for inspecting hex encoded public keys to subkey. The
command looks like:

`subkey inspect --public 0xPUBLICHEX`

* Update client/cli/src/commands/utils.rs

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

substrate/primitives/core/src/crypto.rs

@@ -583,7 +583,17 @@ impl<T: Sized + AsMut<[u8]> + AsRef<[u8]> + Default + Derive> Ss58Codec for T {
 
 /// Trait suitable for typical cryptographic PKI key public type.
 pub trait Public:
-	AsRef<[u8]> + AsMut<[u8]> + Default + Derive + CryptoType + PartialEq + Eq + Clone + Send + Sync
+	AsRef<[u8]>
+	+ AsMut<[u8]>
+	+ Default
+	+ Derive
+	+ CryptoType
+	+ PartialEq
+	+ Eq
+	+ Clone
+	+ Send
+	+ Sync
+	+ for<'a> TryFrom<&'a [u8]>
 {
 	/// A new instance from the given slice.
 	///
@@ -751,6 +761,14 @@ mod dummy {
 		}
 	}
 
+	impl<'a> TryFrom<&'a [u8]> for Dummy {
+		type Error = ();
+
+		fn try_from(_: &'a [u8]) -> Result<Self, ()> {
+			Ok(Self)
+		}
+	}
+
 	impl CryptoType for Dummy {
 		type Pair = Dummy;
 	}
@@ -1108,6 +1126,13 @@ mod tests {
 			&mut []
 		}
 	}
+	impl<'a> TryFrom<&'a [u8]> for TestPublic {
+		type Error = ();
+
+		fn try_from(_: &'a [u8]) -> Result<Self, ()> {
+			Ok(Self)
+		}
+	}
 	impl CryptoType for TestPublic {
 		type Pair = TestPair;
 	}