Extend `snippets` table with `organization_id` field

Problem

See epic description: &13636 (closed)

Task

Extend snippets table with organization_id field (has default value 1, equal to default organization)

Similar to: https://gitlab.com/gitlab-org/gitlab/blob/4ce0cbb6c0da1212357e3036e3d2882c8618fec0/db/migrate/20230822064649_add_organization_id_to_project.rb#L9