Audit Bulker thread should not die silently

org.nuxeo.ecm.platform.audit.service.DefaultAuditBulker use a thread but don't set an uncaught exception handler, so it dies silently on exception.

One must add a thread.setUncaughtExceptionHandler(this::handleUncaughtException); the log level to trace the pb should be SEVERE.

The rational is that if this thread is killed, we keep accumulating log entries without any errors and we will loose them when restarting Nuxeo.

Note that this problem does not affect Nuxeo 9.10 by default because it uses a stream processing so log entries are saved into a Log and are not lost.
That being said it is still possible to configure explicitely the audit to use the bulker writer in 9.10 so it should also be fixed in 9.10.