Draft: PoC N+1 fixes for project dashboard

What does this MR do and why?

This is a set of PoC fixes for each of the remaining known N+1 queries in the project dashboard, see #214037 for more context.

This MR is not for merging but for test failure discovery and to start the discussion on some of these proposed changes. Overview of the changes:

• Eliminates a false positive N+1 by ensuring creator and owner are different in the control set
• Uses Preloaders::UsersMaxAccessLevelInProjectsPreloader to correctly preload the max access level (this wasn't working before)
• Batches merge request counts. This bypasses an existing cache and probably needs to get the same treatment as Project#open_issue_count which uses Projects::BatchOpenIssueCountService
• Changes Gitlab::Cache::Ci::ProjectPipelineStatus to be a drop-in replacement for Ci::Pipeline for the purpose of status rendering and replaces project.last_pipeline with project.pipeline_status

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.