Show Loved polls on beatmapset pages

[cl8n]

for management, this also adds special loved API scope that can't be implied by * and needs to be requested by a designated client

resolves #8202

[notbakaneko]

What's this loved client for, where and how is it going to be used?

Also, all the OAuth-related parts should be separated into a different PR.

[cl8n]

@notbakaneko I put the oauth changes in #9584 , that's ready for review.

I'm gonna mark this one as draft and revisit / probably split it into more manageable parts after figuring out the oauth part.