### 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
}
        public static final CoordinationDiagnosticsDetails EMPTY = new CoordinationDiagnosticsDetails(null, null, null, null, null);
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            if (currentMaster == null) {
                out.writeBoolean(false);
            } else {
                out.writeBoolean(true);
                currentMaster.writeTo(out);
            }
            if (recentMasters == null) {
                out.writeBoolean(false);
            } else {
                out.writeBoolean(true);
                out.writeList(recentMasters);
            }
            out.writeOptionalString(remoteExceptionMessage);
            out.writeOptionalString(remoteExceptionStackTrace);
            if (nodeToClusterFormationDescriptionMap == null) {
                out.writeBoolean(false);
            } else {
                out.writeBoolean(true);
                out.writeMap(nodeToClusterFormationDescriptionMap, StreamOutput::writeString, StreamOutput::writeString);
            }
        }
    }
    
    record RemoteMasterHealthResult(DiscoveryNode node, CoordinationDiagnosticsResult result, Exception remoteException) {}
}