R1:8fe78c9029e5

Conpherence - update the "unread" count in notifications panel aggressively

Summary:
Fixes T7561. Basically everytime we load some transactions in the thread manager, kick off an async thread to update the notification panel.

Should I consolidate this little bit of code into something like this._handleTransactionResponse(r)... ? I just want to keep the JS clear for other engineers and I wasn't sure if that was hiding a bit too much detail.

Test Plan: user a opened durable column. user b sent user a a…