Create an environment for self monitoring project

What does this MR do?

As part of #121719 (closed), we need to be able to view the metrics dashboard for the Self Monitoring project. Loading the metrics dashboard currently depends on the existence of an Environment for the project, so this MR creates an Environment directly after the self-monitoring project itself is created.

This does not address the issue of Gitlab installations that already have the Self Monitoring project created, that will be addressed in a future 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