Conpherence - make sure real time updates still work if you switch threads

Summary: Fixes T8118. Turns out this also was broken in the main view if e.g. you went to just /conpherence/. The fix is to make sure the threadmanager js class explicitly manages subscriptions as the loaded thread changes.

Test Plan:

• from /conpherence/ was able to receive messages in real time.
• from /conpherence/ changed threads and still received messages in real time
• from durable column switched threads and received messages in real time

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8118

Differential Revision: https://secure.phabricator.com/D12758