Keystore overhaul (final) (#13683)

* Introduce keystore specialized sign methods

* Get rid of 'AppKey::UntypedGeneric' associated type.

Untyped generics are accessible using associated types 'Generic' associated type.
I.e. <T as AppKey>::Public::Generic

* Get rid of 'CryptoTypePublicPair'

* Trivial fix

* Small refactory of local keystore implementations

* Remove 'crypto_id' method from 'Public'

* Trivial rename of 'AppKey' to 'AppCrypto'

* Remove unused import

* Improve docs

* Better signature related errors for authority-discovery

* Apply review suggestion

* Apply review suggestions

Co-authored-by: Koute <koute@users.noreply.github.com>

* Authority discoverty signing error revisited

* Signing error revisited for babe and aura as well

* Further cleanup

---------

Co-authored-by: Koute <koute@users.noreply.github.com>

substrate/client/consensus/slots/src/lib.rs

@@ -150,7 +150,7 @@ pub trait SimpleSlotWorker<B: BlockT> {
 		body: Vec<B::Extrinsic>,
 		storage_changes: StorageChanges<<Self::BlockImport as BlockImport<B>>::Transaction, B>,
 		public: Self::Claim,
-		epoch: Self::AuxData,
+		aux_data: Self::AuxData,
 	) -> Result<
 		sc_consensus::BlockImportParams<B, <Self::BlockImport as BlockImport<B>>::Transaction>,
 		sp_consensus::Error,