Add SubscriptionInformation to up-rust usubscription

[matthewd0123]

Hi all!

I have been working on a PR for up-streamer-rust to add the ability for the streamer to track subscriptions, so it can properly route publish-type messages. As part of this, I have created a struct that is used to store and track this information. @AnotherDaniel thought it might be good to keep this information in up-rust instead of directly in the streamer code. I will open a PR with this information. Once the streamer PR is merged, would ask that this code get reviewed.