Fix tracking validator set in ImOnline (#3596)

* Use session::validators instead of staking::current_elected

* Basic test framework.

* Initialize validators, attempt to heartbeat.

* Use dummy crypto for im-online testing.

* Remove printlns.

* Finish test, make it invalid.

* Add reporting test.

* Finalize the test.

* Remove dumbness.

* Updates.

* Update AuRa

* Update srml/im-online/src/tests.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Derive Ord

* Add some more tests.

* Remove stray todo.

* Bump runtime version.

* Bump impl-trait-for-tuples.

* Enforce new version of trait-for-tuples.

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

@@ -213,6 +213,7 @@ macro_rules! app_crypto {
 		}
 
 		impl $crate::RuntimeAppPublic for Public where $public: $crate::RuntimePublic<Signature=$sig> {
+			const ID: $crate::KeyTypeId = $key_type;
 			type Signature = Signature;
 
 			fn all() -> $crate::Vec<Self> {

substrate/core/application-crypto/src/traits.rs

@@ -96,7 +96,10 @@ pub trait RuntimePublic: Sized {
 }
 
 /// A runtime interface for an application's public key.
-pub trait RuntimeAppPublic: Sized {
+pub trait RuntimeAppPublic: Sized  {
+	/// An identifier for this application-specific key type.
+	const ID: KeyTypeId;
+
 	/// The signature that will be generated when signing with the corresponding private key.
 	type Signature: Codec + MaybeDebugHash + Eq + PartialEq + Clone;