Some error improvements (#1956)

* Use `HeaderChainError` in parachains module

* Use MessageProofError instead of 'static str in some places

* Avoid implementing Into<'static str> for some errors

We avoid deriving `Debug` for the structs that we use in the runtime and
we derive `RuntimeDebug` instead in order to avoid bloating th eruntime
with static strs. But implementing `Into<'static str>` does the same. So
in some places it makes sense to replace `Into<'static str>` with `Debug`.

* Move the messages error definition

Move the messages error definition outside of `mod target`

bridges/primitives/header-chain/src/lib.rs

@@ -25,6 +25,7 @@ use bp_runtime::{
 };
 use codec::{Codec, Decode, Encode, EncodeLike, MaxEncodedLen};
 use core::{clone::Clone, cmp::Eq, default::Default, fmt::Debug};
+use frame_support::PalletError;
 use scale_info::TypeInfo;
 #[cfg(feature = "std")]
 use serde::{Deserialize, Serialize};
@@ -36,7 +37,7 @@ pub mod justification;
 pub mod storage_keys;
 
 /// Header chain error.
-#[derive(Clone, Eq, PartialEq, RuntimeDebug)]
+#[derive(Clone, Decode, Encode, Eq, PartialEq, PalletError, Debug, TypeInfo)]
 pub enum HeaderChainError {
 	/// Header with given hash is missing from the chain.
 	UnknownHeader,
@@ -44,15 +45,6 @@ pub enum HeaderChainError {
 	StorageProof(StorageProofError),
 }
 
-impl From<HeaderChainError> for &'static str {
-	fn from(err: HeaderChainError) -> &'static str {
-		match err {
-			HeaderChainError::UnknownHeader => "UnknownHeader",
-			HeaderChainError::StorageProof(e) => e.into(),
-		}
-	}
-}
-
 /// Header data that we're storing on-chain.
 ///
 /// Even though we may store full header, our applications (XCM) only use couple of header