Reduce some EE and builder related ERRO logs to WARN (#3966)

## Issue Addressed

NA

## Proposed Changes

Our `ERRO` stream has been rather noisy since the merge due to some unexpected behaviours of builders and EEs. Now that we've been running post-merge for a while, I think we can drop some of these `ERRO` to `WARN` so we're not "crying wolf".

The modified logs are:

#### `ERRO Execution engine call failed`

I'm seeing this quite frequently on Geth nodes. They seem to timeout when they're busy and it rarely indicates a serious issue. We also have logging across block import, fork choice updating and payload production that raise `ERRO` or `CRIT` when the EE times out, so I think we're not at risk of silencing actual issues.

#### `ERRO "Builder failed to reveal payload"`

In #3775 we reduced this log from `CRIT` to `ERRO` since it's common for builders to fail to reveal the block to the producer directly whilst still broadcasting it to the networ. I think it's worth dropping this to `WARN` since it's rarely interesting.

I elected to stay with `WARN` since I really do wish builders would fulfill their API promises by returning the block to us. Perhaps I'm just being pedantic here, I could be convinced otherwise.

#### `ERRO "Relay error when registering validator(s)"`

It seems like builders and/or mev-boost struggle to handle heavy loads of validator registrations. I haven't observed issues with validators not actually being registered, but I see timeouts on these endpoints many times a day. It doesn't seem like this `ERRO` is worth it.

#### `ERRO Error fetching block for peer     ExecutionLayerErrorPayloadReconstruction`

This means we failed to respond to a peer on the P2P network with a block they requested because of an error in the `execution_layer`. It's very common to see timeouts or incomplete responses on this endpoint whilst the EE is busy and I don't think it's important enough for an `ERRO`. As long as the peer count stays high, I don't think the user needs to be actively concerned about how we're responding to peers.

## Additional Info

NA

Cargo.lock

@@ -4988,6 +4988,7 @@ dependencies = [
  "eth2_ssz",
  "eth2_ssz_types",
  "ethereum-types 0.14.1",
+ "execution_layer",
  "exit-future",
  "fnv",
  "futures",

beacon_node/execution_layer/src/engines.rs

@@ -5,7 +5,7 @@ use crate::engine_api::{
 };
 use crate::HttpJsonRpc;
 use lru::LruCache;
-use slog::{debug, error, info, Logger};
+use slog::{debug, error, info, warn, Logger};
 use std::future::Future;
 use std::sync::Arc;
 use task_executor::TaskExecutor;
@@ -325,7 +325,7 @@ impl Engine {
                 Ok(result)
             }
             Err(error) => {
-                error!(
+                warn!(
                     self.log,
                     "Execution engine call failed";
                     "error" => ?error,

beacon_node/execution_layer/src/lib.rs

@@ -1575,10 +1575,10 @@ impl<T: EthSpec> ExecutionLayer<T> {
                         &metrics::EXECUTION_LAYER_BUILDER_REVEAL_PAYLOAD_OUTCOME,
                         &[metrics::FAILURE],
                     );
-                    error!(
+                    warn!(
                         self.log(),
                         "Builder failed to reveal payload";
-                        "info" => "this relay failure may cause a missed proposal",
+                        "info" => "this is common behaviour for some builders and may not indicate an issue",
                         "error" => ?e,
                         "relay_response_ms" => duration.as_millis(),
                         "block_root" => ?block_root,

beacon_node/http_api/src/lib.rs

@@ -2855,7 +2855,7 @@ pub fn serve<T: BeaconChainTypes>(
                     .await
                     .map(|resp| warp::reply::json(&resp))
                     .map_err(|e| {
-                        error!(
+                        warn!(
                             log,
                             "Relay error when registering validator(s)";
                             "num_registrations" => filtered_registration_data.len(),

beacon_node/network/Cargo.toml

@@ -45,6 +45,7 @@ tokio-util = { version = "0.6.3", features = ["time"] }
 derivative = "2.2.0"
 delay_map = "0.1.1"
 ethereum-types = { version = "0.14.1", optional = true }
+execution_layer =  { path = "../execution_layer" }
 
 [features]
 deterministic_long_lived_attnets = [ "ethereum-types" ]

beacon_node/network/src/beacon_processor/worker/rpc_methods.rs

@@ -7,7 +7,7 @@ use itertools::process_results;
 use lighthouse_network::rpc::StatusMessage;
 use lighthouse_network::rpc::*;
 use lighthouse_network::{PeerId, PeerRequestId, ReportSource, Response, SyncInfo};
-use slog::{debug, error};
+use slog::{debug, error, warn};
 use slot_clock::SlotClock;
 use std::sync::Arc;
 use task_executor::TaskExecutor;
@@ -392,12 +392,26 @@ impl<T: BeaconChainTypes> Worker<T> {
                             break;
                         }
                         Err(e) => {
-                            error!(
-                                self.log,
-                                "Error fetching block for peer";
-                                "block_root" => ?root,
-                                "error" => ?e
-                            );
+                            if matches!(
+                                e,
+                                BeaconChainError::ExecutionLayerErrorPayloadReconstruction(_block_hash, ref boxed_error)
+                                if matches!(**boxed_error, execution_layer::Error::EngineError(_))
+                            ) {
+                                warn!(
+                                    self.log,
+                                    "Error rebuilding payload for peer";
+                                    "info" => "this may occur occasionally when the EE is busy",
+                                    "block_root" => ?root,
+                                    "error" => ?e,
+                                );
+                            } else {
+                                error!(
+                                    self.log,
+                                    "Error fetching block for peer";
+                                    "block_root" => ?root,
+                                    "error" => ?e
+                                );
+                            }
 
                             // send the stream terminator
                             self.send_error_response(