imds: add basic support for Openstack (#44645)

This was tested on OVHCloud. Unfortunately, Nova provides most of the
information (such as IP v6) as a json file with a specific API, so we
rely on the EC2 compat API.

On OVH, the public IP v4 is not in public-ipv4, but in local-ipv4, and
there is no /1.0/meta-data/public-ipv4 URL. From what I know, this is
openstack installation dependant, but public-ipv4 is the documented
place where it should be.

hwdb.d/40-imds.hwdb

@@ -83,6 +83,17 @@ dmi:bvnHetzner:*
  IMDS_KEY_SSH_KEY=/public-keys/0
  IMDS_KEY_USERDATA=/userdata
 
+# https://docs.openstack.org/nova/latest/user/metadata.html
+dmi:*:svnOpenStackFoundation:*
+ IMDS_VENDOR=openstack
+ IMDS_DATA_URL=http://169.254.169.254
+ IMDS_ADDRESS_IPV4=169.254.169.254
+ IMDS_ADDRESS_IPV6=fe80::a9fe:a9fe
+ IMDS_KEY_HOSTNAME=/1.0/meta-data/hostname
+ IMDS_KEY_IPV4_PUBLIC=/1.0/meta-data/public-ipv4
+ IMDS_KEY_SSH_KEY=/1.0/meta-data/public-keys/0/openssh-key
+ IMDS_KEY_USERDATA=/openstack/latest/user_data
+
 # https://docs.oracle.com/en-us/iaas/Content/Compute/Tasks/gettingmetadata.htm#metadata-keys
 dmi:*:catOracleCloud.com:*
  IMDS_VENDOR=oracle-cloud-oci