### 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
String summary,
        CoordinationDiagnosticsDetails details
    ) implements Writeable {
        public CoordinationDiagnosticsResult(StreamInput in) throws IOException {
            this(CoordinationDiagnosticsStatus.fromStreamInput(in), in.readString(), new CoordinationDiagnosticsDetails(in));
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            status.writeTo(out);
            out.writeString(summary);
            details.writeTo(out);
        }
    }
    public enum CoordinationDiagnosticsStatus implements Writeable {
        GREEN,
        UNKNOWN,
        YELLOW,
        RED;
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeEnum(this);
        }
        public static CoordinationDiagnosticsStatus fromStreamInput(StreamInput in) throws IOException {
            return in.readEnum(CoordinationDiagnosticsStatus.class);
        }
    }
    public record CoordinationDiagnosticsDetails(
        DiscoveryNode currentMaster,
        List<DiscoveryNode> recentMasters,
        @Nullable String remoteExceptionMessage,