Update puma config and add binstubs

[mitchellhenke]

Relevant Ticket or Conversation:

Slack thread

Description of Changes:

This PR modifies the Puma config to be more configurable for our potential production use case and changes the defaults to use one thread per process. The application is not confirmed to be thread-safe, and having multiple threads may cause deadlocking or other issues. It is modeled after the changes in the IDP here.

I've also added a few binstubs that would also be useful in production.

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