Add Freeze Period Status

What does this MR do?

During Build creation, this MR looks to see if the current DTTM is within a Freeze Period for this Project. If it is, it adds the $CI_DEPLOY_FREEZE variable. This way, jobs can be bypassed by adding a rule like this:

deploy_to_production:
  stage: deploy
  script: deploy_to_prod.sh
  rules:
    - if: $CI_ENVIRONMENT_FROZEN == null

This feature is a MVC and will be expanded in later releases to drop the build with a message instead of not creating it.

This MR is dependent on !29162 (merged) which adds the underlying data structure.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation - !29384 (merged)
• 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

Part of #214328 (closed)