Reduce log severity for late and unrevealed blocks (sigp#3775)

## Issue Addressed

NA

## Proposed Changes

In sigp#3725 I introduced a `CRIT` log for unrevealed payloads, against @michaelsproul's [advice](sigp#3725 (comment)). After being woken up in the middle of the night by a block that was not revealed to the BN but *was* revealed to the network, I have capitulated. This PR implements @michaelsproul's suggestion and reduces the severity to `ERRO`.

Additionally, I have dropped a `CRIT` to an `ERRO` for when a block is published late. The block in question was indeed published late on the network, however now that we have builders that can slow down block production I don't think the error is "actionable" enough to warrant a `CRIT` for the user.

## Additional Info

NA

beacon_node/execution_layer/src/lib.rs

@@ -1556,7 +1556,7 @@ impl<T: EthSpec> ExecutionLayer<T> {
                         &metrics::EXECUTION_LAYER_BUILDER_REVEAL_PAYLOAD_OUTCOME,
                         &[metrics::FAILURE],
                     );
-                    crit!(
+                    error!(
                         self.log(),
                         "Builder failed to reveal payload";
                         "info" => "this relay failure may cause a missed proposal",

beacon_node/http_api/src/publish_blocks.rs

@@ -5,7 +5,7 @@ use beacon_chain::{
 };
 use lighthouse_network::PubsubMessage;
 use network::NetworkMessage;
-use slog::{crit, error, info, warn, Logger};
+use slog::{error, info, warn, Logger};
 use slot_clock::SlotClock;
 use std::sync::Arc;
 use tokio::sync::mpsc::UnboundedSender;
@@ -72,18 +72,18 @@ pub async fn publish_block<T: BeaconChainTypes>(
             //
             // Check to see the thresholds are non-zero to avoid logging errors with small
             // slot times (e.g., during testing)
-            let crit_threshold = chain.slot_clock.unagg_attestation_production_delay();
-            let error_threshold = crit_threshold / 2;
-            if delay >= crit_threshold {
-                crit!(
+            let too_late_threshold = chain.slot_clock.unagg_attestation_production_delay();
+            let delayed_threshold = too_late_threshold / 2;
+            if delay >= too_late_threshold {
+                error!(
                     log,
                     "Block was broadcast too late";
                     "msg" => "system may be overloaded, block likely to be orphaned",
                     "delay_ms" => delay.as_millis(),
                     "slot" => block.slot(),
                     "root" => ?root,
                 )
-            } else if delay >= error_threshold {
+            } else if delay >= delayed_threshold {
                 error!(
                     log,
                     "Block broadcast was delayed";