Eager load award emoji on notes and participants

What does this MR do?

Reduce the query count of the Issuable#show actions. I've create a MR and Issue both now have 108 notes on them, no award emoji, but even than without this MR it had 340+ queries. I've identified 2 problems:

1. Award Emoji on notes were loaded only when rendering the discussion, thus for each one a query
2. Participants queries the db once per note now too

Why was this MR needed?

N + 1 queries everywhere. 340+ queries should be lowered to below 100 at least.

What are the relevant issue numbers?

Should fix #18408 (closed), also @yorickpeterse @DouweM

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

Progress

Ref	Issue#show	MR#show
master	714	1182
a8be992b	387	unchanged
103e285c	unchanges	1034

The refs above are squashed together in 5b290fd, the head of this branch.