refactor: yield user on enable client helper event listener

[iProdigy]

Prerequisites for Code Changes

• This pull request follows the code style of the project
• I have tested this feature

Changes Proposed

Instead of simple void functions, these enable methods now provide the User on success (which is useful for caching properties like the profile image url to be used in discord embeds)

• enableStreamEventListener(String) => User
• enableStreamEventListener(Iterable<String>) => Collection<User>
• enableFollowEventListener(String) => User
• enableFollowEventListener(Iterable<String>) => Collection<User>

Also:

• Removed 10k limit on channelInformation
• Include channel info in FollowEvent#toString
• Don't invalidate entries in channelInformation cache if the channel was removed from one event listener but is still relevant for the other event listener