IDEA: Convert Hubot to a pure router for Workers calls

[Shadowfiend]

We've been toying for a while with the question of how to move more things to Workers for operational simplicity and reduced spend on the continual running of the worker.

We have a few components of Valkyrie currently running in Cloudflare Workers, but most of the core features still run in the main Hubot process, even if they don't specifically require it (e.g., Discord commands which can be handled via pure HTTP).

The idea here is to instead convert the Hubot process into a pure router, separating the recognition and parsing of pure-chat commands (running in the Hubot process) from the execution and response generation component (running in Workers, with the Hubot process running an HTTP cycle to pull it). This means the Hubot process would focus on filtering "all messages" to "messages that require action" & dispatching and intermediating the Workers interactions. Meanwhile, workers do the heavier lift in a more resource-available environment.

This would also future-proofs us away from any particular chat tool by giving us an intermediary that could massage & forward the same requests to the same backend and massage & forward the same responses back to the chat recipient.