docker.allowed_images can use glob syntax in config.toml

What does this MR do?

I am making "glob (**) available for" allowed-images ".

Ex: config.toml

  [runners.docker]
    allowed_images = ["registry.gitlab.com/**/*:*"]

Formerly I have to write like this.

  [runners.docker]
    allowed_images = ["registry.gitlab.com/*/*:*", "registry.gitlab.com/*/*/*:*", ...]

Why was this MR needed?

GitLab can now handle nested groups and Docker images.

However, if you want to write restrictions with "allowed-images", it is troublesome to write a lot of entries.

Make it possible to use "**" so that you can easily write nested groups and Docker images.

Are there points in the code the reviewer needs to double check?

Yes

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?