Shallow versioning on CI templates for better development process

What does this MR do?

Today, we don't have versioning concept in our CI templates, and because of that, we cannot make any breaking changes today. This significantly limits our development capability and slows our iteration speed.

After the discussion in #17716 (closed), we got some technical proposals. As the beginning of this, we start shallow-versioning with the approach Introduce "stable" and "latest" templates, which was originally proposed by @ayufan

We actually start versioning a template in this MR.

Screenshots

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