### 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
return new CoordinationDiagnosticsResult(CoordinationDiagnosticsStatus.YELLOW, summary, details);
        } else {
            logger.trace("This node thinks the master is unstable, but the master node {} thinks it is stable", master);
            return getMasterIsStableResult(explain, localMasterHistory);
        }
    }
    /**
     * Returns a CoordinationDiagnosticsResult for the case when the master is seen as stable
     * @return A CoordinationDiagnosticsResult for the case when the master is seen as stable (GREEN status, no impacts or details)
     */
    private CoordinationDiagnosticsResult getMasterIsStableResult(boolean explain, MasterHistory localMasterHistory) {
        String summary = "The cluster has a stable master node";
        logger.trace("The cluster has a stable master node");
        CoordinationDiagnosticsDetails details = getDetails(explain, localMasterHistory, null, null);
        return new CoordinationDiagnosticsResult(CoordinationDiagnosticsStatus.GREEN, summary, details);
    }
    /**
     * Returns the health result for the case when we have NOT seen a master recently (at some point in the last 30 seconds).
     * @param localMasterHistory The master history as seen from the local machine
     * @param explain Whether to calculate and include the details in the result
     * @return The CoordinationDiagnosticsResult for the given localMasterHistory
     */
    private CoordinationDiagnosticsResult diagnoseOnHaveNotSeenMasterRecently(MasterHistory localMasterHistory, boolean explain) {
        Collection<DiscoveryNode> masterEligibleNodes = getMasterEligibleNodes();
        final CoordinationDiagnosticsResult result;
        boolean clusterHasLeader = coordinator.getPeerFinder().getLeader().isPresent();
        boolean noLeaderAndNoMasters = clusterHasLeader == false && masterEligibleNodes.isEmpty();
        boolean isLocalNodeMasterEligible = clusterService.localNode().isMasterNode();
        if (noLeaderAndNoMasters) {
            result = getResultOnNoMasterEligibleNodes(localMasterHistory, explain);