Add method to deployment that checks if deployment is a first one for given environment

What does this MR do?

Adds information if deployment is the first one for given environment.

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

Why was this MR needed?

Its required to implement UI differences for first deployment, where some metrics might be incomplete etc.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Related to: https://gitlab.com/gitlab-org/gitlab-ce/issues/40609