Add container registry observations to usage ping

What does this MR do?

Related to #199193 (closed). We want to determine how many self-managed instances are using the GitLab Container Registry (and which version) or a third-party one.

This MR adds new observations about the Container Registry to the Usage Ping payload. More precisely, it adds a new container_registry entry with two attributes, vendor and version. Example:

"container_registry": {
  "vendor": "gitlab",
  "version": "2.9.1-gitlab"
}

The values for these attributes are sourced from the application_settings table, through Gitlab::CurrentSettings.

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

Closes #199193 (closed)