Unlike concatenating strings, this makes sure everything is escaped.
Tests had to be changed because Phoenix.HTML runs attributes through
Enum.sort before generation for whatever reason.

Apply suggestion to test/web/mastodon_api/controllers/account_controller/update_credentials_test.exs

[#2323] Fixed a typo causing /accounts/relationships to render default relationships. Improved the tests.

FollowingRelationship storage & performance optimizations (state turned `ecto_enum`-driven integer, reorganized indices etc.).

Implemented preloading of relationships with parent activities' actors for statuses/timeline rendering. Applied preloading for notifications rendering. Fixed announces rendering issue (preloading-related).

Closes: pleroma/pleroma#1643