Gateway ratelimiting about nostrum

[cookkkie]

Isn't it cleaner to throw if the ratelimit is exceeded? And let the sender handle the retry?

[BobbyMcWho]

Could you use Semaphore to track requests and fail fast when the rate limit has been hit?

[queer]

Given how the gateway ratelimiting is fairly simple, it'd probably make more sense to just use something like https://github.com/ExHammer/hammer

[jchristgit]

We can use (a much simpler method of) the state machine-based approach from #501 to implement this in a relatively simple manner, as the gateway ratelimit is per-connection.

For the session start limit, we will need something different to coordinate it across multiple nodes - likely this belongs to a separate issue. See https://discord.com/developers/docs/topics/gateway#sharding-max-concurrency.

I am planning this for 0.9.