Update minimal size

For development/testing purposes we shouldn't use regular control plane VMs sizes
to save HW resources. For that we need to upgrade  "minimal" value of "openstack_cluster_size"
variable from cookiecutter templates and describe the sizes in reclass-system .
The sizes should be set according to "minimal." flavors from Architecturies document

Minimal size was created by https://gerrit.mcp.mirantis.com/#/c/18279/
for CI and not described in public documentd and no client affected.

Depends-On: https://gerrit.mcp.mirantis.com/#/c/34789/

Change-Id: I8d463080be43aad427d5f6941d721efd76ce156a
Prod-related: PROD-26630 (PROD:26630)
6 files changed