Verify channel constants on startup

[Numerlor]

Description

The bot should check that there are no channels missing from the guild which are present in the bot constants.

Reasoning

As discussed in #342 this will help prevent issues like #335 and has already been implemented for bot.

Proposed Implementation

With the current implementation of the constants as simple classes (not sure why they're NamedTuples) without any annotations or being an object that holds more info about itself, we can check their contents through the vars function and handling any non private names

Another potentially cleaner solution would be changing the classes to something like enums which are iterable and gives us only the values we want without any filtering

Would you like to implement this yourself?

• I'd like to implement this feature myself
• Anyone can implement this feature

Paging @neonSea as they expressed interest in #342

[WillDaSilva]

I'd like to implement this

[WillDaSilva]

I've been playing around with alternatives for NamedTuple for the Channels class. I think it would be best to leave it as a named tuple, as its attributes are used all over the codebase as ints. It could be changed to an IntEnum, whose attributes subclass int, but some errors arise from that since the attributes don't behave exactly like ints do. Changing it to an IntEnum would require calling int on most/all of its uses, which is undesirable. Changing it to a regular Enum would make it difficult to use the attributes as ints at all. Iterating over the __dict__ of the class (via vars) and filtering out anything which begins with an underscore seems like the way to go.