[web] Fetch messages for threads when not in chatList and chatMessageList updates

Summary: When opening sub thread or sidebar that user is not a member of, messages were not fetched

Test Plan: Verify that messages are fetched and displayed correctly

Reviewers: ashoat, palys-swm

Reviewed By: ashoat

Subscribers: zrebcu411, Adrian, atul, subnub, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D689