[native] Left-align pending thread header titles
Summary:
We currently center-align a MessageListHeaderTitle if it is searchEmpty ("New Message" with no users selected), or if it is a pending thread (see definition of areSettingsEnabled).
Center-aligned the header title for pending threads is inconsistent with behavior for normal threads. Discussed this with Ted and @ginsu and we decided it would be more consistent to always left-align, except in the "New Message" case.
Some previous context in D7134. Linear task: ENG-3693
Test Plan:
| before | after |
Reviewers: ginsu, atul
Reviewed By: ginsu
Subscribers: tomek, ginsu
Differential Revision: https://phab.comm.dev/D7474