[web] render thread avatars on chat screen

Summary:
Render thread avatars on chat screen. This includes the chat thread list item, the thread top bar, and and the nav state info bar

This diff won't be landed until avatars is given the green light to be released

Depends on D7209

Test Plan:
Please view the screenshots below to see the changes I made:

Before:

After:

Reviewers: atul, ashoat

Reviewed By: atul

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7210