Chatterino2: Migrate more endpoints from V5 to Helix

[iProdigy]

What should be added?

• [ ] [Kraken getChannel](https://github.com/Chatterino/chatterino2/blob/9a8b85e338ba4fe3b2bb1eee81f3f6f05387959f/src/providers/twitch/api/Kraken.cpp#L10) can be replaced by Helix getChannelInformation (which also retrieves stream title/games for offline channels, but will not work for anonymous users)

• [ ] [TwitchAccount followUser](https://github.com/Chatterino/chatterino2/blob/17aa3f71cd2b154c7016806dca4f03c606007c1c/src/providers/twitch/TwitchAccount.cpp#L291) can use Helix createUserFollows instead of Kraken (note: this will require a new scope user:edit:follows).

• [ ] [TwitchAccount unfollowUser](https://github.com/Chatterino/chatterino2/blob/17aa3f71cd2b154c7016806dca4f03c606007c1c/src/providers/twitch/TwitchAccount.cpp#L309) can use Helix deleteUserFollows instead of Kraken (note: this too requires user:edit:follows).

• [ ] [TwitchChannel refreshCheerEmotes](https://github.com/Chatterino/chatterino2/blob/83b6fad8e6a6ed33972cefd6e9f6a09a773e1cb5/src/providers/twitch/TwitchChannel.cpp#L796) can use Helix getCheermotes instead of Kraken (note: I have heard some reports of this endpoint not returning all emotes in the past - may be fixed now. Also, this can break things for anonymous users).

Why should it be added?
Good to get off deprecated APIs. If breaking things for anonymous users is a no-no, perhaps we could use the Kraken API in one more place while possible to retain the current featureset.

[RAnders00]

going forward, the only way to provide feature to anonymous users is to send the requests via a self-hosted service (https://github.com/Chatterino/api ?) that then uses an app access token.