fix: update nova-compute notification config for telemetry meters

[munirsidd]

Change notification_format from versioned to both so that Ceilometer receives unversioned notifications on the notifications topic and Watcher receives versioned notifications on the versioned_notifications topic [0][1]. Ceilometer already subscribes to both topics [2]. Add notify_on_state_change = vm_and_task_state to enable instance lifecycle notifications like compute.instance.booting.time. Enable instance_usage_audit with an hourly period so nova-compute emits the periodic compute.instance.exists audit events that Ceilometer consumes [3].

[0] - https://docs.openstack.org/watcher/2024.1/configuration/configuring.html#configure-nova-notifications
[1] - https://docs.openstack.org/nova/2024.1/configuration/config.html#notifications.notification_format
[2] - https://opendev.org/openstack/sunbeam-charms/commit/15739a4dbf4245234c2a6348c14654f9c2980156
[3] - https://docs.openstack.org/ceilometer/2024.1/install/install-compute-ubuntu.html#configure-compute-to-use-telemetry

Partial-bug: #2162762

QA steps

1. Deploy sunbeam
2. Enable telemetry

sunbeam enable telemetry

3. Build and install the openstack-hypervisor snap with this branch
   Verify nova-compute config

# in the /var/snap/openstack-hypervisor/common/etc/nova/nova.conf
[DEFAULT]
...
instance_usage_audit = True
instance_usage_audit_period = hour
...
[oslo_messaging_notifications]
driver = messagingv2

[notifications]
notify_on_state_change = vm_and_task_state
notification_format = both

4. Launch an instance and verify compute.instance.booting.time metric

openstack server create --flavor m1.small --image ubuntu --network demo-network test-vm
openstack metric resource show <instance-id>
# Should include compute.instance.booting.time (missing without this fix)

5. Enable Watcher and verify it receives versioned notifications

Links

Jira card: OPEN-4670

[gboutry]

Commits are unsigned

[munirsidd]

Commits are unsigned

Fixed