Remove nio from status server

[cjlarose]

Description

There's a bug related to #2018. Essentially, if the nio4r gem is ever loaded into the puma master process, it makes it impossible to do things like upgrade nio4r during a phased restart and also makes it impossible to remove the gems from disk without breaking phased restarts. Those problems were addressed mostly by my own #2427.

In PR #2427, I was pretty sure I made it so that if you're running a puma cluster with --prune-bundler, the puma master process would never load nio4r. It turns out that actually, if you enable the status server, the puma master process ends up loading nio4r -- the status server is launched in a thread in the master process. Since the status server just uses its own instance of Puma::Server, that ends up using a Reactor, which, in turn requires the nio4r gem.

The user impact is that if you're using the status server,

1. you can't upgrade nio4r in a phased restart
2. you can't safely delete the specific version of the nio4r native extensions from disk from previous releases
3. worker processes unexpectedly double-load the nio4r gem. I don't know what the implications are for this last one, but in general, it's probably not good to double-load any gem.

There are a bunch of different creative solutions to this problem, but I think the easiest is probably to just disable queue_requests for the Puma::Server that serves the status server. Disabling that setting probably doesn't introduce a DOS vector since you probably shouldn't have your puma status server exposed to the public anyway--only trusted clients should have access.

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