Add Security Orchestration Policy Configuration

What does this MR do?

Related to #300220 (closed)

This change adds new model to database to store relationship between Project and Security Orchestration Policy Project where we will store policies as YAML file in repository.

Migrations

⋊> ~/D/g/gitlab on 300220-add-security-orchestration-policy-configuration-model ⨯ 
env VERBOSE=true bundle exec rake db:migrate:up VERSION=20210209160510
== 20210209160510 CreateSecurityOrchestrationPolicyConfigurations: migrating ==
-- create_table(:security_orchestration_policy_configurations, {:comment=>"{\"owner\":\"group::container security\",\"description\":\"Configuration used to store relationship between project and security policy repository\"}"})
   -> 0.0181s
== 20210209160510 CreateSecurityOrchestrationPolicyConfigurations: migrated (0.0219s) 

⋊> ~/D/g/gitlab on 300220-add-security-orchestration-policy-configuration-model ⨯ 
env VERBOSE=true bundle exec rake db:migrate:down VERSION=20210209160510
== 20210209160510 CreateSecurityOrchestrationPolicyConfigurations: reverting ==
-- drop_table(:security_orchestration_policy_configurations, {:force=>:cascade})
   -> 0.0017s
== 20210209160510 CreateSecurityOrchestrationPolicyConfigurations: reverted (0.0046s) 

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team