### Description

The `sendRequest` method is asynchronous and notifies a 
`TransportResponseHandler` when it completes the excecution
(successfully or unsuccessfully). 

When opening the connection we only catch `NodeNotConnectedException`
( https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/transport/TransportService.java#L719 ) which is currently fine as no implementations
throw other type of exception however, it'd be best to catch `Exception` here
so the `handler` gets notified of potential exceptions (as opposed to the caller
having to `try/catch` the call to `sendRequest`)
server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java
} else if (clusterHasLeader) {
            DiscoveryNode currentMaster = coordinator.getPeerFinder().getLeader().get();
            result = getResultOnCannotJoinLeader(localMasterHistory, currentMaster, explain);
        } else if (isLocalNodeMasterEligible == false) { 
            
            result = new CoordinationDiagnosticsResult(
                CoordinationDiagnosticsStatus.RED,
                "No master has been observed recently",
                CoordinationDiagnosticsDetails.EMPTY
            );
        } else { 
            result = diagnoseOnHaveNotSeenMasterRecentlyAndWeAreMasterEligible(
                localMasterHistory,
                masterEligibleNodes,
                coordinator,
                clusterFormationResponses,
                nodeHasMasterLookupTimeframe,
                explain
            );
        }
        return result;
    }
    /**
     * This method handles the case when we have not had an elected master node recently, and we are on a master-eligible node. In this
     * case we look at the cluster formation information from all master-eligible nodes, trying to understand if we have a discovery
     * problem, a problem forming a quorum, or something else.
     * @param localMasterHistory The master history, as seen from this node
     * @param masterEligibleNodes The known master eligible nodes in the cluster
     * @param coordinator The Coordinator for this node
     * @param clusterFormationResponses A map that contains the cluster formation information (or exception encountered while requesting