Create a Project Usage dashboard

[peppepetra]

This is to track the work needed to implement a dashboard that leveraging on the limits metrics give an overview on the resources utilized by a project in OpenStack.

Metrics used:

openstack_cinder_limits_backup_max_gb
openstack_cinder_limits_backup_used_gb
openstack_cinder_limits_volume_max_gb
openstack_cinder_limits_volume_used_gb
openstack_nova_limits_instances_max
openstack_nova_limits_instances_used
openstack_nova_limits_memory_max
openstack_nova_limits_memory_used
openstack_nova_limits_vcpus_max
openstack_nova_limits_vcpus_used
openstack_neutron_network_ip_availabilities_total
openstack_neutron_network_ip_availabilities_used

The dashboard will also list the VMs runnings on the project with some additional info like host, status, ephemeral storage used etc.

Screenshot

[samuelallan72]

Note: patch is proposed at https://review.opendev.org/c/openstack/sunbeam-charms/+/919927