Search for opened MRs - include reopened MRs

What does this MR do?

When an MRs is in reopened state and new commits are pushed to the source branch of that MR new system notes are created, hooks are processed, MRs are marked as WIP in case they should be.

Why was this MR needed?

When MRs was in reopened state it wasn't found when searching for MRs during MR refresh called by UpdateMergeRequestsWorker. This was caused by changes inside merge_requests_for (MergeRequestes::BaseService) made in https://gitlab.com/gitlab-org/gitlab-ce/commit/4eb39e43a85. Before this change a scope opened had been used and this scope includes both opened and reopened states (https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/concerns/issuable.rb#L75). After we started using with_state but specified opened only.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #30291 (closed)