Various minor fixes (#2860)

* Make sr-api-macros benchmark work again

It broke with 4f888f34d3.

* Give better indication of import progress

* Only send consensus info when explicitly enabled

This is only necessary for validators and they can
explicitly enable it via

	--telemetry-url 'wss://telemetry.polkadot.io 1'

(or some other endpoint)

* Remove unnecessary mutable

* Fix style

substrate/core/telemetry/src/lib.rs

@@ -111,7 +111,7 @@ pub const SUBSTRATE_INFO: &str = "0";
 pub const CONSENSUS_TRACE: &str = "9";
 pub const CONSENSUS_DEBUG: &str = "5";
 pub const CONSENSUS_WARN: &str = "4";
-pub const CONSENSUS_INFO: &str = "0";
+pub const CONSENSUS_INFO: &str = "1";
 
 /// Telemetry object. Implements `Future` and must be polled regularly.
 /// Contains an `Arc` and can be cloned and pass around. Only one clone needs to be polled