Adds new event phase Initialization (#5302)

* Adds new event phase `Initialization`

Every event that was deposited inside of `on_initialize` was assigned to
the `ApplyExtrinsic(0)` phase which wasn't correct. This pr introduces a
new phase `Initialization`. This is the new phase while initializing
a block. After initialization we switch to `ApplyExtrinsic(N)` and at
the end to `Finalization` as before.

* Set `ExecutionPhase` in `initialize`

* Increment `spec_version`

substrate/frame/executive/src/lib.rs

@@ -199,6 +199,8 @@ where
 		<frame_system::Module<System>>::register_extra_weight_unchecked(
 			<AllModules as WeighBlock<System::BlockNumber>>::on_finalize(*block_number)
 		);
+
+		frame_system::Module::<System>::note_finished_initialize();
 	}
 
 	/// Returns if the runtime was upgraded since the last time this function was called.