Add openstack-python37-jobs-* templates
Add openstack-python37-jobs-* templates

Create 4 new Python 3.7 project-templates for jobs to use. This
includes base, horizon, neutron, and non-voting variants.

Change-Id: I72619f1d98a17c390661559f598660ecf54a8bca

openstack-infra/openstack-zuul-jobs,openstack-infra/openstack-zuul-jobs