### 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
private CoordinationDiagnosticsResult diagnoseOnMasterHasChangedIdentity(
        MasterHistory localMasterHistory,
        int masterChanges,
        boolean explain
    ) {
        logger.trace("Have seen {} master changes in the last {}", masterChanges, localMasterHistory.getMaxHistoryAge());
        CoordinationDiagnosticsStatus coordinationDiagnosticsStatus = CoordinationDiagnosticsStatus.YELLOW;
        String summary = String.format(
            Locale.ROOT,
            "The elected master node has changed %d times in the last %s",
            masterChanges,
            localMasterHistory.getMaxHistoryAge()
        );
        CoordinationDiagnosticsDetails details = getDetails(explain, localMasterHistory, null, null);
        return new CoordinationDiagnosticsResult(coordinationDiagnosticsStatus, summary, details);
    }
    /**
     * This returns CoordinationDiagnosticsDetails.EMPTY if explain is false, otherwise a CoordinationDiagnosticsDetails object
     * containing only a "current_master" object and a "recent_masters" array. The "current_master" object will have "node_id" and "name"
     * fields for the master node. Both will be null if the last-seen master was null. The "recent_masters" array will contain
     * "recent_master" objects. Each "recent_master" object will have "node_id" and "name" fields for the master node. These fields will
     * never be null because null masters are not written to this array.
     * @param explain If true, the CoordinationDiagnosticsDetails will contain "current_master" and "recent_masters". Otherwise it will
     *                be empty.
     * @param localMasterHistory The MasterHistory object to pull current and recent master info from
     * @return An empty CoordinationDiagnosticsDetails if explain is false, otherwise a CoordinationDiagnosticsDetails containing only
     * "current_master" and "recent_masters"
     */
    private static CoordinationDiagnosticsDetails getDetails(
        boolean explain,