perf(likes): limit likes relationship results

[SychO9]

Supersedes #3585

Changes proposed in this pull request:
Similar to #3780, it limits the results of the likes relationship of a post, and paginates all results in the existing modal.
The PR makes sure that the actor ID is in the limited results of the relationship, so that we can show the proper translation value that has You liked and others....

Reviewers should focus on:
Changes here are based on the linked PR, so they can only be merged after that.

Screenshot

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

[luceos]

Looking good, even seeing improvements locally with the discuss data.