upcloud: add server groups and target port for lb (#9831)

contrib/terraform/upcloud/README.md

contrib/terraform/upcloud/cluster-settings.tfvars

contrib/terraform/upcloud/main.tf

contrib/terraform/upcloud/modules/kubernetes-cluster/main.tf

...terraform/upcloud/modules/kubernetes-cluster/variables.tf

.../terraform/upcloud/modules/kubernetes-cluster/versions.tf

contrib/terraform/upcloud/sample-inventory/cluster.tfvars

contrib/terraform/upcloud/variables.tf

contrib/terraform/upcloud/versions.tf