Mark own thumbsups/downs on MR and issues overviews

What does this MR do?

Mark own thumbsups and thumbsdowns on MergeRequest and Issues overview pages so you don't have to (re)check every single one just to see you've already voted.

Why was this MR needed?

Solves Issue #14746 (moved)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• [not needed] Documentation created/updated
• [not needed] API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• [please check] Conform by the merge request performance guides
• [please check] Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

#14746 (moved)