Add expand/migrate/contract migrations for CI
This patch adds equivalent expand/migrate/contract migration scripts for
Community Images. The expand migration
'ocata_expand01_add_visibility.py' creates a new migration branch 'expand'
from the last known migration i.e., 'mitaka02'. Similarly, the contract
migration 'ocata_contract01_drop_is_public.py' creates another new
migration branch called 'contract' from the last known migration.
The data migration 'ocata_migrate01_community_images.py' migrates
all rows in the database at once. There is possibility of performance
degradation while the data migrations are running.
Partially-Implements: blueprint database-strategy-for-rolling-upgrades
Co-Authored-By: Hemanth Makkapati <firstname.lastname@example.org>