Add 'query-events' command to QMP to query async events
Sometimes it is neccessary for an application to determine
whether a particular QMP event is available, so they can
decide whether to use compatibility code instead. This
introduces a new 'query-events' command to QMP to do just
that
* monitor.c: Turn MonitorEvent -> string conversion
into a lookup from a static table of constant strings.
Add impl of qmp_query_events monitor command handler
* qapi-schema.json, qmp-commands.hx: Define contract of
query-events command
Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>