### 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
/*
             * If the cancellableReference for this poll attempt is equal to remoteCoordinationDiagnosisTask, then that means that
             * this poll attempt is the current one. If they are not equal, that means that
             * cancelPollingRemoteMasterStabilityDiagnostic() has been called on this poll attempt but this thread is not yet
             * aware. So we cancel the Cancellable in cancellableReference if it is not null. Note that
             * remoteCoordinationDiagnosisTask can be null.
             */
            if (cancellableReference.equals(remoteCoordinationDiagnosisTask)) {
                /*
                 * Because this is not synchronized with the cancelPollingRemoteMasterStabilityDiagnostic() method, there is a
                 * slim chance that we will add a task here for a poll that has already been cancelled. But when it completes and runs
                 * rescheduleDiagnosticsFetchConsumer() we will then see that remoteCoordinationDiagnosisTask does not equal
                 * cancellableReference, so it will not be run again.
                 */
                try {
                    DiscoveryNode masterEligibleNode = getMasterEligibleNodes().stream().findAny().orElse(null);
                    cancellableReference.set(
                        fetchCoordinationDiagnostics(
                            masterEligibleNode,
                            responseConsumer.andThen(rescheduleDiagnosticsFetchConsumer(responseConsumer, cancellableReference))
                        )
                    );
                } catch (EsRejectedExecutionException e) {
                    if (e.isExecutorShutdown()) {
                        logger.trace("Not rescheduling request for cluster coordination info because this node is being shutdown", e);
                    } else {
                        throw e;
                    }
                }
            } else {