[native] render thread avatars for parent/child threads in thread settings

Summary:
rendered thread avatars for both parent and child threads in thread settings

Test Plan:
Please check out these screenshots to see the changes I made:

staff user:

non staff user:

Reviewers: ashoat, atul

Reviewed By: ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7137