[EE] Refactor the way we pass `old associations` to issuable's update services

CE MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15542

What does this MR do?

Improves the architecture to pass around associations' previous values in IssuableBaseService.

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

Why was this MR needed?

Because the methods signature were started to become quite long.

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Review
  • 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

What are the relevant issue numbers?

Closes #40226