Protected containers: Add basic model and migrations

What does this MR do and why?

• This MR is related to issue Protected containers: Add basic model and migra... (#424367 - closed).
• This MR introduces the basic backend components for protecting containers, e.g. database migration, model, etc.
• The scope of the basic functionality was discussed in the epic: &9825
• This MR intends to follow the implementation the MR for the feature "protected packages", see Protected packages: Add model and migration for... (!124776 - merged)

🛠 with ❤ at Siemens

Screenshots or screen recordings

No visuals to show. This MR contains mostly backend -related code, see the next section

How to set up and validate locally

1. rails db:migrate
2. Open the rails console (rails c) and start playing around with the new model

ContainerRegistry::Protection::Rule.create!(
  project: Project.find_by_full_path("flightjs/Flight"),
  container_path_pattern: "flightjs/flight/*",
  push_protected_up_to_access_level: Gitlab::Access::OWNER
)

Todos

• Rename factory for container registry protecftion rule

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

  • Changelog entry added, if necessary
  • Documentation created/updated via this MR
  • Documentation reviewed by technical writer or follow-up review issue created
  • Tests added for this feature/bug
  • Tested in all supported browsers
  • Conforms to the code review guidelines
  • Conforms to the merge request performance guidelines
  • Conforms to the style guides
  • Conforms to the javascript style guides
  • Conforms to the database guides

Related to #424367 (closed)