Introduce sign_with method in keystore (#4925)

* Add KEY_KIND_ID to the public trait

This change is being introduced for the purpose of identifying a public
key with it's identifier and algorithm "kind".

* Use `sign_with` as implemented in BareCryptoStore

* Implement `sign_with` in sc_keystore

* Fix inconsistencies, use *_KIND_ID in sp_core testing

* Rename KeyKindId to CryptoTypeId

* Remove pair-returning functions from BareCryptoStore trait

* Define CryptoTypeId in app-crypto macros

* Add functions to get keys supported by keystore

* Fix sign_with signature to include CryptoTypePublicPair

* Add `sign_with_any` and `sign_with_all`

* Use keystore.sign_with in auth_discovery

* Rename get_supported_keys -> supported_keys

* Added headers to function docstrings

* Use chain instead of extending a temp vector

* Fixed some code formatting

* Restrict size of CryptoTypeId

This is to be able to use Encode/Decode derives and the overcome having
the size being unknown at compile-time.

* Implement sign_with in the trait itself

* Remove whitespace

* Use key_type also as a CryptoTypeId in app_crypto macros

* Rename `get_keys` to `keys` in BareCryptoStore

* Remove usage of key_pair funcs in tests

* Adjust docstring for *_CYPTO_ID constants

* Fix failures

* Simplify mapping on keys

* Remove one let

* Fixed typo

* PR feedback

* remove whitespace

* Zip keys and signatures

* Use into_iter & remove cloned

* Pass index to MissingSignature

* Use typed errors instead of strings for BareCryptoStore

* Implement Debug for trait error

* Use hashsets for better performance for supported_keys

* Make sure keys are inserted into the keystore

* Make sign_with_all return type consistent with `sign_with`

* Rename Error to BareCryptoStoreError

* Rename CRYPT_TYPE_ID -> CRYPTO_ID

* Remove unnecessary CRYPTO_ID declaration in Public trait

* Convert pub key to CryptoTypePublicPair

* Fix use

* Fix code style

* Implement From on CryptoTypePublicPair in app_crypto macros

* Change CryptoTypePublicPair to a struct

* Implement Display on CryptoTypePublicPair

* Pass CryptoTypePublicPair to MissingSignature error

* Adjust docs according to function signature

* Unify keys implementation

* Fix RPC author tests

* Fix stackoverflow

* Tabify spaces

* Pass KeyTypeId to error for easier debugging

* Fix asserts

* Use ToHex to format public key

* Use constants from sp_core

* Rename testing KeyTypeId constants

* Please compiler

* Restore KeyTypeId names

apparently, they're not only used in tests

* Use BareCryptoStoreError instead of String

* Document return value

* Fix borrow check

* Convert to hashset internally

* WIP - iter_keys

* Return raw_public_keys

* Address PR feedback

* Address PR Feedback

* Fix hexdisplay import error

* Update primitives/core/src/traits.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/primitives/core/src/sr25519.rs

@@ -39,7 +39,7 @@ use crate::crypto::{
 #[cfg(feature = "std")]
 use crate::crypto::Ss58Codec;
 
-use crate::{crypto::{Public as TraitPublic, UncheckedFrom, CryptoType, Derive}};
+use crate::crypto::{Public as TraitPublic, CryptoTypePublicPair, UncheckedFrom, CryptoType, Derive, CryptoTypeId};
 use crate::hash::{H256, H512};
 use codec::{Encode, Decode};
 use sp_std::ops::Deref;
@@ -54,6 +54,9 @@ use sp_runtime_interface::pass_by::PassByInner;
 #[cfg(feature = "full_crypto")]
 const SIGNING_CTX: &[u8] = b"substrate";
 
+/// An identifier used to match public keys against sr25519 keys
+pub const CRYPTO_ID: CryptoTypeId = CryptoTypeId(*b"sr25");
+
 /// An Schnorrkel/Ristretto x25519 ("sr25519") public key.
 #[cfg_attr(feature = "full_crypto", derive(Hash))]
 #[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Encode, Decode, Default, PassByInner)]
@@ -390,6 +393,18 @@ impl TraitPublic for Public {
 	}
 }
 
+impl From<Public> for CryptoTypePublicPair {
+    fn from(key: Public) -> Self {
+        (&key).into()
+    }
+}
+
+impl From<&Public> for CryptoTypePublicPair {
+    fn from(key: &Public) -> Self {
+        CryptoTypePublicPair(CRYPTO_ID, key.to_raw_vec())
+    }
+}
+
 #[cfg(feature = "std")]
 impl From<MiniSecretKey> for Pair {
 	fn from(sec: MiniSecretKey) -> Pair {
@@ -599,7 +614,7 @@ impl CryptoType for Pair {
 #[cfg(test)]
 mod compatibility_test {
 	use super::*;
-	use crate::crypto::{DEV_PHRASE};
+	use crate::crypto::DEV_PHRASE;
 	use hex_literal::hex;
 
 	// NOTE: tests to ensure addresses that are created with the `0.1.x` version (pre-audit) are