add sync committee contribution timeout (sigp#3291)

## Issue Addressed

Resolves sigp#3276. 

## Proposed Changes

Add a timeout for the sync committee contributions at 1/4 the slot length such that we may be able to try backup beacon nodes in the case of contribution post failure.

## Additional Info

1/4 slot length seemed standard for the timeouts, but may want to decrease this to 1/2.

I did not find any timeout related / sync committee related tests, so there are no tests. Happy to write some with a bit of guidance.

common/eth2/src/lib.rs

@@ -110,6 +110,7 @@ pub struct Timeouts {
     pub liveness: Duration,
     pub proposal: Duration,
     pub proposer_duties: Duration,
+    pub sync_committee_contribution: Duration,
     pub sync_duties: Duration,
 }
 
@@ -121,6 +122,7 @@ impl Timeouts {
             liveness: timeout,
             proposal: timeout,
             proposer_duties: timeout,
+            sync_committee_contribution: timeout,
             sync_duties: timeout,
         }
     }
@@ -907,7 +909,12 @@ impl BeaconNodeHttpClient {
             .push("validator")
             .push("contribution_and_proofs");
 
-        self.post(path, &signed_contributions).await?;
+        self.post_with_timeout(
+            path,
+            &signed_contributions,
+            self.timeouts.sync_committee_contribution,
+        )
+        .await?;
 
         Ok(())
     }

validator_client/src/lib.rs

@@ -72,6 +72,7 @@ const HTTP_ATTESTER_DUTIES_TIMEOUT_QUOTIENT: u32 = 4;
 const HTTP_LIVENESS_TIMEOUT_QUOTIENT: u32 = 4;
 const HTTP_PROPOSAL_TIMEOUT_QUOTIENT: u32 = 2;
 const HTTP_PROPOSER_DUTIES_TIMEOUT_QUOTIENT: u32 = 4;
+const HTTP_SYNC_COMMITTEE_CONTRIBUTION_TIMEOUT_QUOTIENT: u32 = 4;
 const HTTP_SYNC_DUTIES_TIMEOUT_QUOTIENT: u32 = 4;
 
 const DOPPELGANGER_SERVICE_NAME: &str = "doppelganger";
@@ -280,6 +281,8 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
                         liveness: slot_duration / HTTP_LIVENESS_TIMEOUT_QUOTIENT,
                         proposal: slot_duration / HTTP_PROPOSAL_TIMEOUT_QUOTIENT,
                         proposer_duties: slot_duration / HTTP_PROPOSER_DUTIES_TIMEOUT_QUOTIENT,
+                        sync_committee_contribution: slot_duration
+                            / HTTP_SYNC_COMMITTEE_CONTRIBUTION_TIMEOUT_QUOTIENT,
                         sync_duties: slot_duration / HTTP_SYNC_DUTIES_TIMEOUT_QUOTIENT,
                     }
                 } else {