Small mostly doc improvements (#4661)

* Better docs on non initialized state.

* Document better what is happening.

* More precise errors.

* cargo fmt

polkadot/node/core/chain-selection/src/lib.rs

@@ -352,6 +352,7 @@ async fn run<Context, B>(
 		match res {
 			Err(e) => {
 				e.trace();
+				// All errors right now are considered fatal:
 				break
 			},
 			Ok(()) => {

polkadot/node/core/dispute-coordinator/src/real/mod.rs

@@ -390,11 +390,13 @@ where
 			},
 			FromOverseer::Signal(OverseerSignal::BlockFinalized(_, _)) => {},
 			FromOverseer::Communication { msg } =>
-			// Note: It seems we really should not receive any messages before the first
-			// `ActiveLeavesUpdate`, if that proves wrong over time and we do receive
-			// messages before the first `ActiveLeavesUpdate` that should not be dropped,
-			// this can easily be fixed by collecting those messages and passing them on to
-			// `Initialized::new()`.
+			// NOTE: We could technically actually handle a couple of message types, even if
+			// not initialized (e.g. all requests that only query the database). The problem
+			// is, we would deliver potentially outdated information, especially in the event
+			// of bugs where initialization fails for a while (e.g. `SessionInfo`s are not
+			// available). So instead of telling subsystems, everything is fine, because of an
+			// hour old database state, we should rather cancel contained oneshots and delay
+			// finality until we are fully functional.
 				tracing::warn!(
 					target: LOG_TARGET,
 					?msg,