Fix slow loading of chatrooms (ChatMain issue)

[taoeffect]

Problem

Since updating to 1.2.0, in our GIG group, on mobile, the chatroom takes 12 seconds to load, every time I switch to it from some other chatroom.

Solution

It seems like there are multiple possible problems:

1. IIRC, the chatroom state should be cached in vuex, so switching to it should be instant. This should be fixed.
2. Even if the cache got broken somehow, this is way too long to load the chatroom. It seems like it's probably loading the entire thing each time. Explore Think more deeply about how Chatroom contracts are sync'd. #1784 as a possible solution to fixing this.